Thermoelectric Management Unit

ABSTRACT

Embodiments of the invention provide a thermal management unit including a housing, at least one fan, a plurality of thermoelectric modules, at least one heat sink assembly coupled to the plurality of thermoelectric modules, and controller providing power to the plurality of thermoelectric modules. The thermal management unit also includes a printed circuit board incorporating the plurality of thermoelectric modules and electrically connecting the plurality of thermoelectric modules to the controller. The printed circuit board separates an ambient side of the thermal management unit and an enclosure side of the thermal management unit.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Patent Application Nos. 61/146,593, filed on Jan. 22, 2009and 61/172,266, filed on Apr. 24, 2009, the entire contents of which areincorporated herein by reference.

BACKGROUND

Thermal management units, such as air conditioning and heating units,are used to cool and heat electrical enclosures. Most conventionalthermal management units use compressors. However, thermoelectric (TE)devices can convert electrical current into heating or cooling based onthe Peltier effect and are generally much more efficient thancompressors.

Electrical circuits that provide electrical current to the TE devicesare often housed in junction boxes separate from the thermal managementunits. These junction boxes are bulky and take up an excessive amount ofspace within the electrical enclosures.

SUMMARY

Some embodiments of the invention provide a thermal management unit foran enclosure. The thermal management unit includes a housing, at leastone fan to direct air flow through the housing, a plurality ofthermoelectric modules, at least one heat sink assembly coupled to theplurality of thermoelectric modules, and controller providing power tothe plurality of thermoelectric modules. The thermal management unitalso includes a printed circuit board incorporating the plurality ofthermoelectric modules and electrically connecting the plurality ofthermoelectric modules to the controller. The printed circuit boardseparates an ambient side of the thermal management unit and anenclosure side of the thermal management unit. The plurality ofthermoelectric modules can include a first plurality of thermoelectricmodules positioned in an area of higher air flow in the housing and asecond plurality of thermoelectric modules position in an area of lowerair flow in the housing. The controller can provide higher power to thefirst plurality of thermoelectric modules and lower power to the secondplurality of thermoelectric modules.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an ambient side of a thermoelectric(TE) management unit according to one embodiment of the invention.

FIG. 1B is a perspective view of an enclosure side of the TE managementunit of FIG. 1A.

FIGS. 2A-2D are top, front, side, and back views of a TE management unitaccording to one embodiment of the invention.

FIG. 3 is a perspective view of a heat sink assembly including a TEmodule, an enclosure heat sink, and an ambient heat sink for use in theTE management unit of FIGS. 1A and 1B.

FIGS. 4A-4E are perspective and various side views of the heat sinkassembly of FIG. 3.

FIGS. 5A-5F are perspective and various views of alternate head sinksfor use with the TE management unit.

FIGS. 6A-6B are tables of performance values for a phase change material(PCM) for use in the interface between the TE module and the heat sinksof FIG. 3.

FIGS. 7A, 7B, and 7C are side views of a TE management unit positionedhalf inside and half outside an enclosure, outside an enclosure, andinside an enclosure, respectively.

FIGS. 8A-8D are block wiring diagrams of electrical configurations of TEmodules in a thermoelectric management unit according to someembodiments of the invention.

FIG. 9 is a block diagram of a controller for use with a TE managementunit according to one embodiment of the invention.

FIGS. 10A-10J are a block diagram and electrical schematics of a controlcircuit of the controller of FIG. 9.

FIGS. 11A-11E are a block diagram and electrical schematics of a powercircuit of the controller of FIG. 9.

FIG. 12 is a wiring schematic of components of the TE management unit.

FIG. 13 is a top view of a printed circuit board for use with the TEmanagement unit according to one embodiment of the invention.

FIGS. 14A-14G are flow charts of a control scheme according to oneembodiment of the invention for use with the TE management unit.

FIG. 15A is a perspective view of an ambient side of a TE managementunit according to another embodiment of the invention.

FIG. 15B is a perspective view of an enclosure side of the TE managementunit of FIG. 15A.

FIG. 16 is a perspective view of a separator printed circuit boardincluding a plurality of heat sink assemblies for use with the TEmanagement unit of FIGS. 15A-15B.

FIG. 17 is a front view of an enclosure side of the separator printedcircuit board of FIG. 16.

FIG. 18 is a front view of an ambient side of the separator printedcircuit board of FIG. 16.

FIGS. 19A-19H are a block diagram and electrical schematics of a powercircuit according to another embodiment of the invention for use with aTE management unit.

FIGS. 20A-20I are a block diagram and electrical schematics of a controlcircuit according to another embodiment of the invention for use with aTE management unit.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “supported,” and “coupled” and variationsthereof are used broadly and encompass both direct and indirectmountings, connections, supports, and couplings. Further, “connected”and “coupled” are not restricted to physical or mechanical connectionsor couplings.

The following discussion is presented to enable a person skilled in theart to make and use embodiments of the invention. Various modificationsto the illustrated embodiments will be readily apparent to those skilledin the art, and the generic principles herein can be applied to otherembodiments and applications without departing from embodiments of theinvention. Thus, embodiments of the invention are not intended to belimited to embodiments shown, but are to be accorded the widest scopeconsistent with the principles and features disclosed herein. Thefollowing detailed description is to be read with reference to thefigures, in which like elements in different figures have like referencenumerals. The figures, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope ofembodiments of the invention. Skilled artisans will recognize theexamples provided herein have many useful alternatives and fall withinthe scope of embodiments of the invention.

FIGS. 1A and 18 illustrate a thermoelectric (TE) management unit 10according to one embodiment of the invention. The TE management unit 10can be used to cool and/or heat an electrical enclosure 12 (as shownschematically in FIGS. 7A-7C) or other enclosed space. As shown in FIGS.2A-2D, the TE management unit 10 can include a housing 14 with anenclosure (e.g., internal) side 16 and an ambient (e.g., external) side18. The enclosure side 16 can be used to condition air in the enclosure12. If the TE management unit 10 is being used to cool the enclosure 12,the enclosure side 16 and the ambient side 18 can be considered a coldside and a warm side, respectively. If the TE management unit 10 isbeing used to warm the enclosure 12, the enclosure side 16 and theambient side 18 can be considered a warm side and a cold side,respectively. In addition, the enclosure side 16 can include anenclosure air inlet 11 (as shown in FIG. 2C) and an enclosure air outlet13 and the ambient side can include an ambient air inlet 15 (as shown inFIG. 2B) and an ambient air outlet 17 (as shown in FIG. 2D). In someembodiments, the housing 14 can be a NEMA type 12, 3R, 4, or 4X housingconstructed of stainless steel. In one embodiment, the housing 14 can becoated with a light grey (e.g., RAL 7035) semi-texture paint.

As shown in FIG. 1A, the TE management unit 10 can include one or moreheat sink assemblies 20. The number of heat sink assemblies 20 candepend on the necessary cooling or heating capacity of the TE managementunit 10. As shown in FIGS. 3 and 4A-4E, each heat sink assembly 20 caninclude an ambient heat sink 22 and an enclosure heat sink 24. In someembodiments, the enclosure heat sink 24 can be smaller than the ambientheat sink 22. The ambient heat sink 22 can be coupled to the enclosureheat sink 24 with fasteners 25, such as bolts and washers, or attachedin another suitable manner. One suitable type of heat sink that can beused for the ambient heat sink 22 and/or the enclosure heat sink 24, asshown in FIGS. 5A-5F, is sold by AAVID Thermalloy.

As shown in FIG. 3, each heat sink assembly 20 can include a TE module26 positioned between the ambient heat sink 22 and the enclosure heatsink 24. The TE module 26 can include two wires 28, 30. When a voltageis applied to the wires 28, 30, the TE module 26 can transfer heat fromone side of the TE management unit 10 (e.g., the ambient side 18) to theother side of the TE management unit 10 (e.g., the enclosure side 16).Due to the TE management unit 10 using the TE modules 26 rather than acompressor, as used in conventional thermal management units, the TEmanagement unit 10 can be easier to manufacture and also easier toservice after installation. In addition, the TE management unit 10 canbe substantially quieter compared to conventional units that usecompressors. The TE management unit 10 can also be used for condensatemanagement in the enclosure 12.

In one embodiment as shown in FIGS. 1A and 1B, the TE management unit 10includes twelve separate heat sink assemblies 20 coupled to a panel 32.The panel 32 can include twelve apertures through which the heat sinkassemblies 20 can be positioned. Depending on the thermal (i.e., coolingor heating) capacity necessary for a particular application, the TEmanagement unit 10 can include any suitable number of heat sinkassemblies 20. In some embodiments, the thermal capacity of the TEmanagement unit 10 can range from about 100 watts to about 1000 watts.Table 1 below lists approximate cooling capacities and approximate unitsizes for TE management units 10 according to some embodiments of theinvention.

TABLE 1 Nominal Cooling Capacity and Nominal Unit Size Nominal CoolingNominal Unit Size Capacity (height × width × depth) 100 Watts  5.5″ ×12″ × 6″ 200 Watts  5.5″ × 12″ × 6″ 300 Watts  7.0″ × 15.5″ × 8″ 400Watts  9.0″ × 17.5″ × 8″ 600 Watts  9.0″ × 17.5″ × 8″ 800 Watts  9.0″ ×17.5″ × 8″ 1000 Watts  11.0″ × 23.5″ × 10″

The TE management unit 10 can include one or more ambient fans 34coupled to the panel 32 (which are illustrated as fan housings in FIG.1A). As shown in FIGS. 1A and 2C, the ambient fans 34 can move air fromthe ambient inlet 15, across the ambient heat sinks 22, and out theambient outlet 17, away from the TE management unit 10, creating anambient air loop. As shown in FIG. 1B, the TE management unit 10 canalso include one or more enclosure fans 36. As shown in FIGS. 1B and 2C,the enclosure fans 36 can move air from the enclosure inlet 11, acrossthe enclosure heat sinks 24, and out the enclosure outlet 13 to feedconditioned air back into the enclosure 12, creating an enclosure airloop. In some embodiments, the ambient fans 34 and/or the enclosure fans36 can be impeller fans.

The heat sink assemblies 20 can be designed in a modular fashion so thatany suitable number of heat sink assemblies 20 can be used to achievethe desired thermal capacity. The modular heat sink assemblies 20 canalso minimize the effects of shear forces that occur in the TE modules26, as compared to conventional, larger heat sink assemblies that arecoupled to multiple TE modules. Since the colder side of the TE module26 will contract in size and the warmer side of the TE module 26 willexpand in size, large heat sinks attached to multiple TE modules tend toexperience shear stresses, warping, and the loss of physical contact,and thus, the loss of efficient thermal transfer with some of the TEmodules. Also, when large heat sinks warp, gaskets between the heat sinkand the enclosure can start to leak, allowing water from outdoors toleak inside the enclosure.

Using the modular heat sink assemblies 20 can help minimize the effectsof shear stresses and warping at the interface between the TE modules 26and the heat sinks 22, 24. A phase change material (PCM), or othersuitable thermal transfer material, can also be used at the interfacebetween the TE modules 26 and the heat sinks 22, 24. The PCM can enhancethermal transfer. Once suitable PCM is sold by Berquist under the brandHi-Flow® 225U, as described in the tables of FIGS. 6A-6B.

The housing 14 can be a side-mount type unit and can be rack-mounted tothe enclosure 12. In other embodiments, the housing 14 can be mounted tothe enclosure 12 via other suitable mounting methods. FIG. 7Aillustrates the TE management unit 10 with the ambient side 18positioned outside of the enclosure 12 and the enclosure side 16positioned inside the enclosure 12 (i.e., a partial recess unit). FIG.7B illustrates both the ambient side 18 and the enclosure side 16positioned outside the enclosure 12 (i.e., a full exterior unit), withthe enclosure air inlet 11 and enclosure air outlet 13 positioned sothat the enclosure fans 36 can pull air from the enclosure 12 throughthe enclosure air loop. FIG. 7C illustrates both the ambient side 18 andthe enclosure side 16 positioned inside the enclosure 12 (i.e., a fullrecess unit), with the ambient air inlet 15 and ambient air outlet 17positioned so that the ambient fans 34 can pull air from outside theenclosure 12 through the ambient air loop.

In some embodiments, the modular design concept is based on using thesingle panel 32 that incorporates the TE modules 26. The TE modules 26can be ganged together in order to provide the TE management unit 10with increased thermal capacity. More specifically, each TE module 26configuration can have a wiring scheme that allows the TE managementunit 10 to achieve a maximum combination of efficiency and thermalpower. FIGS. 8A-8B illustrate wiring options for TE module sets withsixteen TE modules 26. In a configuration with sixteen TE modules 26,the air distribution may not even be across all sixteen TE modules 26,and there may be areas of higher flow and areas of lower flow. Thesixteen TE module stack can be configured as two, three, or fourseparate strings to allow a control system to achieve maximum benefitsof thermal power and efficiency by providing more or less power to eachstring. The TE management unit 10 can include lower power TE modules 26in an area of lower air flow and higher power TE modules 26 in an areaof higher air low. In this manner, each TE module 26 can achieve ahigher level of efficiency, with the net result a higher efficiency ofthe entire thermal unit. For a three-string configuration, since sixteenTE modules cannot be evenly divided by three, multiple uneven stringscan be used (e.g., two strings of five TE modules 26 and one string ofsix TE modules 26). FIGS. 8C-8D illustrate wiring options for TE modulesets with twelve and eight TE modules 26, respectively.

Fan power has a large effect on efficiency of the TE management unit 10,and fan speed has a large affect on fan power. The fans 34, 36, as wellas the TE modules 26, can be monitored and controlled to achieve maximumefficiency at all combinations of temperatures. In some embodiments ofthe invention, the speed of the fans 34, 36 can be varied (e.g., insubstantially real-time) based on a combination of inputs to acontroller 38 to maximize efficiency given a particular thermal load.The thermal transfer, or thermal load, can be determined by measuring atemperature difference across the TE modules 26. The controller 38 canincorporate this information into a programmed algorithm to set theoptimum fan speed for each combination of power input, cooling output,ambient temperature, and enclosure temperature. Fan speed can becontrolled using pulse width modulation (PWM) control with a tachometeroutput to monitor status and, in some embodiments, the ambient fans 34can be controlled separately from the enclosure fans 36. In addition,power to the TE modules 26 can be controlled to vary the thermaltransfer of the TE management unit 10.

In some embodiments, the approach to variable control can be to adjustthe TE module power based on the thermal load required. Normal fancontrol options for this approach can be as follows: (1) let both theenclosure and ambient fans run full speed; (2) let the enclosure fan runfull speed and speed control the ambient fans based on external air intemperature or air out temperature; (3) let the external fan run fullspeed and speed control the ambient fan based on a temperaturedifference that is set at a fixed value; and (4) speed control both theenclosure and ambient fans, as described in the previous paragraph. Thecontrol of the fans 34, 36 and the TE modules 26 according to someembodiments of the invention is further described below with respect tothe flowcharts of FIGS. 13A-13G.

FIG. 9 illustrates the controller 38 according to one embodiment of theinvention. The controller 38 can include a control circuit 39, as shownin FIGS. 10A-10J, and a power circuit 41, as shown in FIGS. 11A-11E. Theelectrical circuits of FIGS. 10A-10J and 11A-11E can be incorporatedinto a separate junction box or control board that is positionedremotely from the TE management unit 10. In one embodiment, the controlcircuit 39 can be housed in one junction box and the power circuit 41can be housed in another, separate junction box.

As shown in FIG. 10A, the control circuit 39 can include a temperaturesensor circuit 40 (further illustrated in FIG. 10B), a fan speed controlcircuit 42 (further illustrated in FIG. 10C), a tachometer circuit 44(further illustrated in FIG. 10D), an alarms circuit 46 (furtherillustrated in FIG. 10E), a serial port 48 (further illustrated in FIG.10F), a memory/external interface circuit 50 (further illustrated inFIG. 10G), a programming interface 52 (further illustrated in FIG. 10H),a power monitor circuit 54 (further illustrated in FIG. 10I), and amicrocontroller circuit 56 (further illustrated in FIG. 10J). In oneembodiment, these components can be connected as shown by theconnections in FIG. 10A as described below.

FIG. 10B illustrates the temperature sensor circuit 40 of the controlcircuit 39. The temperature sensor circuit 40 can include fourtemperature sensors S1-S4. The temperature sensors S1-S4 can bethermistors (e.g., 10 kilo-ohm thermistors with a 1% tolerance),thermocouples, or similar devices. Each temperature sensor S1-S4 canhave an accompanying sensor circuit including three resistors and onecapacitor: Resistors R1-R3 and capacitor C1 for sensor S1; resistorsR4-R6 and capacitor C2 for sensor S2; resistors R7-R9 and capacitor C3for sensor S3; and resistors R10-R12 and capacitor C4 for sensor S4. Insome embodiments, resistors R1, R4, R7, and R10 can be about 232kilo-ohms with a 1% tolerance, resistors R2, R5, R8, and R11 can beabout 1 kilo-ohm with a 1% or 5% tolerance, and resistors R3, R6, R9,and R12 can be about 10 kilo-ohms with a 1% or 5% tolerance. Inaddition, capacitors C1-C4 can have a capacitance of about 0.1microfarads. Resistors R1-R12, as well as all other resistors describedherein, can be provided using incorporated resistor packs, such as DIP(dual in-line) packages. Each accompanying sensor circuit can alsoinclude an input voltage V1. In one embodiment, the voltage V1 is about3.3 volts.

The first sensor circuit, including sensor S1, can be routed to themicrocontroller circuit 56 via a connection 58. The second sensorcircuit, including sensor S2, can be routed to the microcontrollercircuit 56 via a connection 60. The third sensor circuit, includingsensor S3, can be routed to the microcontroller circuit 56 via aconnection 62. Finally, the fourth sensor circuit, including sensor S4,can be routed to the microcontroller circuit 56 via a connection 64.

The temperature sensors S1-S4 can be remotely mounted in various airflowregions (e.g., of the housing 14) for temperature control. For example,one of the temperature sensors (S1, for example) can be positioned atthe enclosure inlet 11 and another temperature sensor (S2, for example)can be positioned at the enclosure outlet 13. A third temperature sensor(S3, for example) can be positioned at the ambient inlet 15 and a fourthtemperature sensor (S4, for example) can be positioned at the ambientoutlet 17. Therefore, temperatures can be sensed at both the inlets andoutlets of the enclosure air loop and the ambient air loop. In someembodiments, the temperature sensors S1-S4 can have a temperatureaccuracy of about +/−2 degrees Celsius. In addition, in someembodiments, the controller 38 can have an operational temperature rangeof about minus 40 degrees Celsius to about 80 degrees Celsius.

FIG. 10C illustrates the fan speed control circuit 42 of the controlcircuit 39. The fan speed control circuit 42 can operate servomotors foreach fan 34, 36. In some embodiments, PWM speed control can be used tooperate the servomotors (i.e., via the fan speed control circuit 42),and open collector tachometers can be used for feedback (i.e., via thetachometer circuit 44, described with respect to FIG. 10D), allowingfull closed-loop digital control for the fans 34, 36. The fan speedcontrol circuit 42 can connect to PWM inputs for each fan. For example,a connection 66 can lead to a PWM input for a first ambient fan 34, aconnection 68 can lead to a PWM input for a second ambient fan 34, aconnection 70 can lead to a PWM input for a first enclosure fan 36, anda connection 72 can lead to a PWM input for a second enclosure fan 36.

As shown in FIG. 10C, the controller 38 can independently speed controleach of the four fans 34, 36 separately. To speed control the firstambient fan 34 (via the connection 66), a PWM signal from themicrocontroller circuit 56 is transmitted to a resistor R13 via aconnection 74 and can switch on and off a transistor Q1. The base of thetransistor Q1 can be connected to the resistor R13 and the emitter ofthe transistor Q1 can be connected to ground. When the signal fromconnection 74 applies a substantial cut-in voltage across thebase-emitter junction, the transistor Q1 becomes active and allowscurrent flow from the collector to the emitter. The current is conductedfrom a voltage source V2 (e.g., about 15 volts), through resistors R14and R15, and through the collector and the emitter to ground. Theconnection 66 is connected between the resistors R14 and R15 to providethe PWM input to the first ambient fan 34 when the transistor Q1 is on.This method is used to speed control the second ambient fan 34, and thefirst and second enclosure fans 36 as well, via PWM inputs toconnections 76, 78, and 80, respectively, from the microcontrollercircuit 56. The resistor R13, and resistors R16, R19, and R22, can beabout 100 ohms. The resistor R14, and resistors R17, R20, and R23, canbe about 100 kilo-ohms. The resistor R15, and resistors R18, R21, andR24, can be about 100 ohms. The transistor Q1, and transistors Q2, Q3,and Q4, can be NPN, BJT transistors, such as Part No. 2N222,manufactured by Fairchild Semiconductors®, among others.

The fans 34, 36 can be modulated from minimum to maximum control points.For example, the enclosure fans 36 can be operated between 75% and 100%of their maximum speed and the ambient fans 34 can be operated between25% and 100% of their maximum speed. In one embodiment, the maximumspeed for both the enclosure fans 36 and the ambient fans 34 can beabout 4900 rotations per minute (RPM). In another embodiment, theenclosure fans 36 can operate at or above about 3000 RPM and the ambientfans 34 can operate at or above about 1000 RPM. In some embodiments, thefans 34, 36 can be digitally stable up to 4 kilo-Hertz controlfrequency.

FIG. 10D illustrates the tachometer circuit 44 of the control circuit39. The tachometer circuit 44 can receive outputs from open collectortachometers (not shown) in connection with the fans 34, 36 to monitorfan speed. The controller 38 can use the outputs from the tachometercircuit 44 to adjust the PWM inputs to the fans 34, 36, if necessary.The tachometer circuit 44 can convert the tachometer outputs (in pulsesper revolution) to frequencies in hertz to analyze the fan speeds (e.g.,using a timer to determine a period between rising edges of thetachometer outputs). A calculated tachometer frequency in hertz can beequal to one to six pulses per revolution, depending on a gain valueused. For example, in one embodiment, the tachometer frequency from theambient fans 34 can be equal to four pulses per revolution (i.e., thegain value is four), while the tachometer frequency from the enclosurefans 36 can be equal to one pulse per revolution (i.e., the gain valueis one). The tachometer outputs can be referenced to a power return lineof the fans 34, 36.

As shown in FIG. 10D, a connection 82 can be connected to a tachometeroutput of the first ambient fan 34, a connection 84 can be connected toa tachometer output of the second ambient fan 34, a connection 86 can beconnected to a tachometer output of the first enclosure fan 36, and aconnection 88 can be connected to a tachometer output of the secondenclosure fan 36. Each tachometer output connection 82, 84, 86, 88 canhave an accompanying circuit including two resistors and one capacitorleading to a multiplexer U1: Resistors R25-R26 and capacitor C5 for theconnection 82, leading to pin 4 of the multiplexer U1; resistors R27-R28and capacitor C6 for the connection 84, leading to pin 3 of themultiplexer U1; resistors R29-R30 and capacitor C7 for the connection86, leading to pin 2 of the multiplexer U1; and resistors R31-R32 andcapacitor C8 for the connection 88, leading to pin 1 of the multiplexerU1. The resistors, R25, R27, R29, and R31 can each be about 100kilo-ohms. The resistors R26, R28, R30, and R32 can each be about 1kilo-ohms. The capacitors C5-C8 can be about 0.01 microfarads.

The multiplexer U1 can be an 8-input multiplexer, such as Part No.74HC151, manufactured by Philips Semiconductors. Pins 1-4, which can becoupled to connections 82, 84, 86, and 88 can be multiplexer inputs ofthe multiplexer U1. Pins 12-14 can also be multiplexer inputs and canreceive outputs from various override devices, such as smoke detectors,door switches, etc., which the control circuit 39 can monitor. In FIG.10D, pins 14 and 15 are connected to override devices (not shown), whilepins 12 and 13 are left open. For example, an input signal from theoverride device at a connection 90 is transmitted through a resistor R33to a regulator U2 (i.e., a voltage regulator) and a return connection tothe override device can be at a connection 92. A positive output fromthe regulator U2 creates a voltage at resistor R34 from voltage V1,sending a positive voltage to pin 15 of the multiplexer U1. A similarcircuit for pin 14 of the multiplexer U1 can include an input connection94, a return connection 96, resistors R35-R36, and a regulator U3. Theresistors R34 and R36 can each be about 100 kilo-ohms. In someembodiments, the resistors R33 and R35 can depend on the override deviceto which they are connected. In one example, the resistors R33 and R35can be about 1 kilo-ohm and about 100 ohms, respectively.

The multiplexer U1 also receives an enable input at pin 7 from themicrocontroller circuit 56 via a connection 98. In addition, selectinputs to pins 9, 10, and 11 of the multiplexer U1 are routed from themicrocontroller circuit 56 via connections 100, 102, and 104,respectively. The output of the multiplexer, at pin 5, is routed to themicrocontroller circuit 56 via a connection 106. The select inputs(connections 100, 102, and 104 from the microcontroller circuit 56) canalso be routed to the alarm circuit 46, as shown in FIG. 10E.

FIG. 10E illustrates the alarm circuit 46 of the control circuit 39. Thealarm circuit 46 can include four independent, optically-isolated,open-collector outputs for remote alarm output detection. For example, afirst alarm (not shown) can be connected via an input connection 108 anda return connection 110, a second alarm (not shown) can be connected viaan input connection 112 and a return connection 114, a third alarm (notshown) can be connected via an input connection 116 and a returnconnection 118, and a fourth alarm (not shown) can be connected via aninput connection 120 and a return connection 122. Alarm outputs can becontrolled via a latch U4. As shown in FIG. 10E, the input connection toeach alarm is connected to the latch U4 via a resistor, a regulator, andanother resistor, and the return connection for each alarm is connectionthrough the regulator to ground. Thus, the first alarm is connected tothe latch U4 at pin 4 via resistors R37 and R38 and a regulator U5, thesecond alarm is connected to the latch U4 at pin 5 via resistors R39 andR40 and a regulator U6, the third alarm is connected to the latch U4 atpin 6 via resistors R41 and R42 and a regulator U7, and the fourth alarmis connected to the latch U4 at pin 7 via resistors R43 and R44 and aregulator U8. If the latch U4 outputs a high logic level at any of pins4-7, the respective alarm will be activated, indicating a fault in theTE management unit 10. If the latch U4 outputs a low logic level, thereis no fault and the alarm is not activated. In some embodiments,resistors R38, R40, R42, and R44 can each be about 330 ohms, resistorsR37 and R39 can each be about 100 ohms, and resistors R41 and R43 caneach be about 1 kilo-ohm.

The latch U4 can also provide output signals to remote devices, such asslave units. For example, pins 9 and 10 can be connected to remote unitsvia connections 124 and 126, through resistors R45 and R46,respectively. Both resistors R45 and R46 can have a resistance of about330 ohms. The remote units can also be connected to a reference voltageV1 via a connection 128, and ground via a connection 130. The latch U4can also output signals to alarm light emitting diodes (LEDs) via pins11 and 12. For example, two LEDS, D1 and D2, can be used to communicatealarm outputs. In one embodiment, D1 is a green LED and D2 is a red LED.If an alarm function is active (i.e., if a fault has occurred), D1 canbe switched off and D2 can be switched on. If the alarm function is notactive, the D1 can be switched on and D2 can be switched be off. TheLEDs D1 and D2 can be connected to pins 11 and 12 through resistors R47(about 100 ohms) and R48 (about 100 kilo-ohms), respectively.

The latch U4 can be an 8-bit addressable latch, such as part no.74HC259, manufactured by Philips Semiconductors. Address inputs to pins1, 2, and 3 can be from the connections 104, 102, and 100, respectively,from the microctroller circuit 40 (the connections 104, 102, and 100 arealso routed to the tachometer circuit 44). An enable input to pin 14 ofthe latch U4 can be received from the microcontroller circuit 56 via aconnection 132. Pin 15 can be a conditional reset input, which is activewhen low, and can be connected to the voltage V1. Pin 13 can receiveinput data from the microcontroller circuit 56 via a connection 134.

Various faults can activate alarm outputs for the alarms. Faults thatcan activate the first, second, and third alarms, in some embodiments,are described below.

The first alarm output can be an airflow alarm, caused by failing fans(e.g., a fan fault) or an excessive temperature change across theenclosure or ambient airflow loops (e.g., a temperature delta fault).Ambient or enclosure temperature delta faults can occur when a measuredtemperature across the TE module 26 is greater than about 15 degreesCelsius. If this occurs, the controller 38 can, in addition toactivating the first alarm output, reset the TE power to about zero andramp the power back up to a steady state value. If there is an enclosuretemperature delta fault, the controller 38 can also run the enclosurefans 36 at maximum speed. Similarly, if there is an ambient temperaturedelta fault, the controller 38 can also run the ambient fans 34 atmaximum speed. Additionally, if any fan 34, 36 fails, the controller 38can run all other functioning fans 34, 36 at maximum speed.

The second alarm output can be a temperature or sensor failure alarm,due to a failing sensor (e.g., a sensor fault) or an exceeded enclosurehigh or low temperature limit as measured by the enclosure inlettemperature sensor S1 (e.g., a temperature fault). For example, a hightemperature alarm can be activated when a temperature sensor (theenclosure inlet temperature sensor S1, for example), is about 10 degreesCelsius above the cooling set-point and a low temperature alarm can beactivated when the temperature sensor (also the temperature sensor S1,for example) is about 10 degrees Celsius below the heating set-point.Plus or minus about 10 degrees Celsius can be a factory default for thehigh and low temperature limits and can be adjusted by a user. A sensorfault can occur, and the second alarm can be activated, if anytemperature sensor S1-S4 reads less than about minus 50 degrees Celsiusor greater than about 85 degrees Celsius. If either of these conditionsis measured, it can be assumed that the temperature sensor in question(i.e., S1, S2, S3, or S4) has failed and, in addition to the secondalarm, the controller 38 can set the TE voltage to about 18 volts,direct current (Vdc) and set the fans 34, 36 to maximum speed.

A third alarm output can be a power fault alarm, which can be triggeredby power faults (e.g., if the controller input voltage is out of range,the fan voltage or current is out of range, or if the TE module voltageor current is out of range). For example, a power fault can be triggeredif the TE current (i.e., the current to the TE modules 26) is greaterthan about 20 amperes, direct current, or the voltage is greater thanabout 24 Vdc. If such an event occurs, the controller 38 can reset theTE module power to zero and ramp the power back up to a steady statevalue, and run the fans 34, 36 at maximum speed. In another example, apower fault can be triggered if the fan current (i.e., the current tothe fans 34, 36) is greater than about 4 amperes, direct current. Ifsuch an event occurs, the controller 38 can reset the fan power to zeroand ramp the voltage back up to about 12 Vdc.

The controller 38 can have a delay period (e.g., thirty seconds orfifteen seconds) for alarm outputs to minimize nuisance alarms. Any ofthe alarms can be on and stable for the full delay period to activatethe output and display functions when the delay period has beenexceeded. For any faults, the controller 38 can either continue normaloperation, or go to a max ON condition (e.g., by setting the TE modulevoltage to about 18 Vdc and the fans 34, 36 to maximum speed). In someembodiments, alarm pull-ups can be provided to reset the alarms. Thepull-ups can be referenced to the return connections of the alarms(e.g., the connections 110, 114, 118, and 122) and can have maximumparameters of about 5 milli-amperes and about 80 Vdc.

FIG. 10F illustrates the serial port 48 of the control circuit 39. Theserial port 48 can be an external communication link for themicrocontroller circuit 56 to communicate with an outside source (e.g.,an external computer) for automated test functions, data logging, etc.In one embodiment, the serial port 48 can allow RS-232 communicationbetween the microcontroller circuit 56 and the outside source. Theserial port 48 can receive signals from the microcontroller circuit 56via a connection 136 and can transmit signals to the microcontrollercircuit 56 via a connection 138. The serial port 48 can also have apower connection, using the voltage V1, and a ground connection. Theoutside source can command the controller 38 via the serial port 48 torun in a manual mode and begin automated testing. The outside source canfurther command the controller 38 back into normal mode to continuenormal operation after, or during, testing. For example, the outsidesource can manually override control temperatures to force the TEmanagement unit 10 to run in a certain test state. The outside sourcecan send a request to receive all controller data during or after thetest. Data from past operations can be collected and/or data can becollected in near real-time. The data can be processed by the outsidesource to determine the results of the test. If, while connected to theoutside source and a command is not received for a time period, such as15 seconds, the controller 38 can revert back to normal mode. In someembodiments, the serial port 48 can be an “I2C” communications port, anRS-232 port, an RS-485 port, a USB port, or an Ethernet port.

FIG. 10G illustrates the memory/external interface circuit 50 of thecontrol circuit 39. The memory/external interface circuit 50 can includea memory chip U9 and connection port J1. The memory chip U9 can be aSEEPROM (serial EEPROM) chip. The connection port J1 can be used toconnect an external device, such as a display board. “I2C”communications can be used for communication between the microcontrollercircuit 56, the memory chip U9, and the connection port J1 viaconnections 140 and 142. For example, I2C communications can be usedwith the memory chip U9 for loading and storing controller runtimevariables and logging faults. In some embodiments, the connection 140can be a data line and the connection 142 can be a clock line. Also,resistors R49 and R50, both about 1 kilo-ohm, can be included in thememory/external interface circuit 50, connecting the voltage V1 toconnections 140 and 142, respectively.

FIG. 10H illustrates the programming interface 52 of the control circuit39. The programming interface 52 can include a reprogramming port J2 toallow reprogramming of a microcontroller U10 (as shown in FIG. 10J)within the microcontroller circuit 56 once the TE management unit 10 isalready installed. Five pins of the reprogramming port J2 can beconnected to the microcontroller circuit 56 via connections 144, 146,148, 150, and 152, three pins be connection to ground, and two pins canbe connected to voltage source V1. One of the two pins connected to thevoltage source V1 is connected via a resistor R51 (e.g., about 47.5kilo-ohms).

FIG. 10I illustrates the power monitor 54 of the control circuit 39. Thepower monitor 54 amplifies various voltages from the power circuit 41(as shown in FIGS. 11A-11E) and inputs the amplified voltages to themicrocontroller circuit 56 for monitoring purposes. For example, avoltage V3 (described later) is amplified via amplifier A1 and connectedto the microcontroller circuit 56 via a connection 154. A voltage V4 isamplified via amplifier A2 and connected to the microcontroller circuit56 via a connection 156. A voltage V5 is amplified via amplifier A3 andresistors R52 (e.g., 1 kilo-ohm), R53 (e.g., 100 ohms), and R54 (e.g.,33 kilo-ohms) and connected to the microcontroller circuit 56 via aconnection 158. A voltage V6 is amplified via amplifier A4 and resistorsR55 (e.g., 1 kilo-ohm), R56 (e.g., 1.8 kilo-ohms), and R57 (e.g., 1kilo-ohm) and connected to the microcontroller circuit 56 via aconnection 160.

FIG. 10J illustrates the microcontroller circuit 56 of the controlcircuit 39. The microcontroller circuit 56 can incorporate themicrocontroller U10, which can include a microprocessor and/or a digitalsignal processor, a digital-to-analog converter, and ananalog-to-digital converter. In some embodiments, the microcontrollerU10 can be a digital signal controller, such as Part No. MC56F8025,manufactured by Freescale Semiconductor®. The following paragraphsdescribe pin assignments for the microcontroller U10 according to oneembodiment of the invention.

The connection 136, which is the receiving line of the serial port 48,can be connected to pin 1 of the microcontroller U10. The connection142, which is the clock line of the I2C bus line to the memory circuit50, can be connected to pin 2 of the microcontroller U10. The connection138, which is the transmission line of the serial port 48, can beconnected to pin 3 of the microcontroller U10. The connection 106, whichis the output of the multiplexer U1 in the tachometer circuit 44, can beconnected to pin 4 of the microcontroller U10. Pin 5 of themicrocontroller U10 can be connected to a voltage divider circuitincluding the voltage V1, a resistor R58 (e.g., about 10 kilo-ohms), anda resistor R59 (e.g., about 10 kilo-ohms). The connection 160, which isan amplified voltage signal of the voltage V6 from the power monitorcircuit 54, can be connected to pin 6 of the microcontroller U10. Theconnection 154, which is an amplified voltage signal of the voltage V3from the power monitor circuit 54, can be connected to pin 7 of themicrocontroller U10. The connection 156, which is an amplified voltagesignal of the voltage V4 from the power monitor circuit 54, can beconnected to pin 8 of the microcontroller U10. The connection 132, whichis the enable input for the latch U4 of the alarm circuit 46, can beconnected to pin 9 of the microcontroller U10. The connection 98, whichis the enable input for the multiplexer U1 of the tachometer circuit 44,can be connected to pin 10 of the microcontroller U10. Pins 11, 29, 35,16, 23, and 12, 17, 28, and 36 of the microcontroller U10 can beconnected to a capacitor circuit including capacitors C9-C13 inconnection with the voltage V1 (at pins 11, 29, 35, 16, and 23) andground (at pins 12, 17, 28, and 36), with the configuration shown inFIG. 10J. The capacitors C9 and C11 can have a capacitance of about 1microfarad, the capacitors C10 and C12 can have a capacitance of about0.1 microfarads, and the capacitor C13 can have a capacitance of about10 microfarads.

The connection 64, which is an input from the temperature sensor S4, canbe connected to pin 13 of the microcontroller U10. The connection 62,which is an input from the temperature sensor S3, can be connected topin 14 of the microcontroller U10. The connection 60, which is an inputfrom the temperature sensor S2, can be connected to pin 15 of themicrocontroller U10. The connection 58, which is an input from thetemperature sensor S1, can be connected to pin 16 of the microcontrollerU10. The connection 146 from the programming interface 52 can beconnected to pin 19 of the microcontroller U10. The connection 104,which can lead to inputs in both the tachometer circuit 44 and the alarmcircuit 46, can be connected to pin 20 of the microcontroller U10. Theconnection 152 from the programming interface 52 can be connected to pin21 of the microcontroller U10. The microcontroller U10 can output avoltage V7 (described below), at pin 22, to the power circuit 41. Themicrocontroller U10 can output another voltage V8 (described below), atpin 23, to the power circuit 41. The microcontroller U10 can outputanother voltage V9 (described below), at pin 24, to the power circuit41.

The connection 158, which is an amplified voltage signal from thevoltage V5 from the power monitor circuit 54, can be connected to pin 25of the microcontroller U10. The connection 134, which is the data inputline to the latch U4 in the alarm circuit 46, can be connected to pin 26of the microcontroller U10. The connection 100, which can lead to inputsto both the tachometer circuit 44 and the alarm circuit 46, can beconnected to pin 27 of the microcontroller U10. The connection 140,which is the data line of the I2C bus line to the memory/externalinterface 50, can be connected to pin 30 of the microcontroller U10. Themicrocontroller U10 can output another voltage V10 (described below), atpin 31, to the power circuit 41. The connection 78, which is the PWMinput to the first enclosure fan 36, can be connected to pin 32 of themicrocontroller U10. The connection 80, which is the PWM input to thesecond enclosure fan 36, can be connected to pin 33 of themicrocontroller U10. The connection 76, which is the PWM input to thesecond ambient fan 34, can be connected to pin 39 of the microcontrollerU10. The connection 74, which is the PWM input to the first ambient fan34, can be connected to pin 40 of the microcontroller U10. Theconnection 150 from the programming interface 52 can be connected to pin41 of the microcontroller U10. The connection 102, which can lead toinputs to both the tachometer circuit 44 and the alarm circuit 46, canbe connected to pin 42 of the microcontroller U10. The connection 144from the programming interface 52 can be connected to pin 43 of themicrocontroller U10. The connection 148 from the programming interface52 can be connected to pin 44 of the microcontroller U10.

FIG. 11A illustrates the power circuit 41. The power circuit 41 caninclude a fan power circuit 162 (further illustrated in FIG. 11B), a TEpower circuit 164 (further illustrated in FIGS. 11C and 11D), and a unitpower circuit 166 (further illustrated in FIG. 11E).

FIG. 11B illustrates the fan power circuit 162. In some embodiments,each fan 34, 36 can include four connections: power in connections,return power connections, tachometer outputs (as described with respectto the tachometer circuit 44 above), and PWM inputs (as described withrespect to the fan speed control circuit 42 above). The power in andreturn power connections can provide or remove power to the fans 34, 36.The power in and return power connections, as shown in FIG. 11B, canreceive DC power from a switcher circuit controlled by themicrocontroller U10. The voltage V8 from the microcontroller U10, whichis an oscillating (i.e., PWM) signal, and the voltage V1 turn ontransistors Q5 and Q6, which can switch on a high-side gate driver U11to provide a boosted voltage (i.e., the voltage V2) to a gate of MOSFETQ7. Input to a drain of the MOSFET Q7 can come from the unit powercircuit 166, described below, via a connection 168. The voltage V2 canbe provided through a diode D3 (rated for 100 volts, 1 ampere) to thehigh-side gate driver U11 and also to charge a capacitor C14 (e.g., 1.0microfarads, rated for 100 volts). When the high-side gate driver U11 isswitched off, the capacitor C14 can still provide a boosted voltage tothe MOSFET Q7. Resistors R60-R62 can provide a voltage divider circuitfor the transistors Q5 and Q6. The resistors R60, R61, and R62 can be2.1 kilo-ohms, 1 kilo-ohm, and 1 kilo-ohm, respectively. The switchercircuit can also include resistors R63 (e.g., 47.5 kilo-ohms), R64 (10kilo-ohms), R65 (15 ohms), and C15 (47 microfarads, rated for 25 volts).

Following the source of the MOSFET Q7 can be an inductor-capacitorcircuit including voltage clamping diode D4, a parallel inductor L1(e.g., 47 micro-henries, rated for 2.7 amperes), and parallel capacitorsC16 (e.g., 0.1 microfarads, rated for 100 volts) and C17 (e.g., 1500microfarads, rated for 35 volts). Following the inductor-capacitorcircuit can be the input line to the power in connections for the fans34, 36 (four fans in total), and the circuit can be completed via thereturn power connections from the fans 34, 36 (e.g., to ground). Forexample, power in to the first enclosure fan 36 can be received atconnection 170 and return through connection 172, power in to the secondenclosure fan 36 can be received at connection 174 and return throughconnection 176, power in to the first ambient fan 34 can be received atconnection 178 and return through connection 180, and power in to thesecond ambient fan 34 can be received at connection 182 and returnthrough connection 184. In some embodiments, the tachometers (i.e., fromthe tachometer circuit 44) are connected to the return power connections172, 176, 180, and 184 to determine the speed of the fans 34, 36.

A voltage divider including resistors R66 (e.g., 100 kilo-ohms) and R67(e.g., 6.34 kilo-ohms) can provide the feedback voltage V3 to the powermonitor circuit 54. The microcontroller U10 can use an amplified signalof the voltage V3 to monitor an output of the switching circuit andadjust the oscillating PWM signal (i.e., the voltage V8) accordingly.Also included after the return power connection is sensing resistor R68(e.g., 0.005 ohms) and capacitor C18 (e.g., 0.1 microfarads, rated for50 volts). The voltage V5 of the power return connection, can bedirected to the power monitor circuit 54 for monitoring. For example, iftoo much current is being conducted through resistor R68, as would beseen by the voltage V5, the controller 38 can limit the input voltageV8. In addition, a voltage V11 can be monitored at the power inconnections. The input voltage V8 can be a fixed voltage and canregulate a desired output voltage to the fans 34, 36 within about +/−1.0Vdc. In some embodiments, the desired output voltage at the power inconnections to the fans 34, 36 can be about 12.0 Vdc, with an outputcurrent up to about 2.7 amperes.

FIGS. 11C-11D illustrate the TE power circuit 164. The TE power circuit164 can provide power to the TE modules 26. The TE power circuit 164 canhave a first switching circuit, similar to the fan power circuit 162,which can withstand higher power inputs. The circuits of FIGS. 11C and11D are connected via connections 186 and 188.

As shown in FIG. 11C, the voltage V7 from the microcontroller U10, whichis an oscillating (i.e., PWM) signal, and the voltage V1 can turn ontransistors Q8 and Q9, which can switch on a high-side gate driver U12to provide a boosted voltage (i.e., the voltage V2) to a gate of MOSFETQ10. Input to a drain of the MOSFET Q10 can come from the unit powercircuit 166, described below, via the connection 168. The voltage V2 canbe provided through a diode D5 (e.g., rated for 100 volts, 1 ampere) tothe high-side gate driver U12 and also to charge a capacitor C19 (e.g.,1.0 microfarads, rated for 100 volts). When the high-side gate driverU12 is switched off, the capacitor C19 can still provide a boostedvoltage to the MOSFET Q10. Resistors R69-R71 can provide a voltagedivider circuit for the transistors Q8 and Q9. In addition, when thehigh-side gate driver U12 is switched on, power can be provided tocharge the capacitor C19 via the voltage V10 from the microcontrollerU10 and a circuit including resistors R72-R75, schottke diodes D6 andD7, zener diode D8, capacitor C20, and transistor Q11. As a result, aboosted voltage can be provided to the drain of the MOSFET Q10 at alltimes, whether the driver U12 is switched on or off.

The resistors R69, R73, and R75 can be about 2.1 kilo-ohms, theresistors R70 and R71 can be about 1 kilo-ohm, the resistor R72 can beabout 330 ohms, and the resistor R74 can be about 100 kilo-ohms. Thecapacitor C20 can be about 1.0 microfarads (rated for 100 volts) and thezener diode D8 can have a 15-volt breakdown voltage. The switchercircuit can also include resistors R76 (e.g., 47.5 kilo-ohms), R77 (10kilo-ohms), R78 (15 ohms), and C21 (47 microfarads, rated for 25 volts).

Following the source of the MOSFET Q10 can be an inductor-capacitorcircuit including voltage clamping diode D9, a parallel inductor L2(e.g., 220 micro-henries, rated for 27 amperes), and parallel capacitorsC22 (e.g., 0.1 microfarads, rated for 100 volts), C23 (e.g., 2700microfarads, rated for 35 volts), and C24 (e.g., 2700 microfarads, ratedfor 35 volts). Following the inductor-capacitor circuit can be a voltagedivider including resistors R79 (e.g., 100 kilo-ohms) and R80 (e.g.,6.34 kilo-ohms) that provides the feedback voltage V4 to the powermonitor circuit 54. The microcontroller U10 can use an amplified signalof the voltage V4 to monitor an output of the switching circuit andadjust the oscillating PWM signal (i.e., voltage V7) accordingly. Alsofollowing the inductor-capacitor circuit are resistor R81 (e.g., 0.002ohms), resistor R82 (e.g., 0.002 ohms) and capacitor C25 (e.g., 0.1microfarads, rated for 50 volts). The inductor-capacitor circuit,through the resistors R81-R82 and the capacitor C25, leads to theconnections 186 and 188.

As shown in FIG. 11D, the TE power circuit 164 includes an H-bridge withtwo identical circuits. The voltage V2 is provided to high-side gatedrivers U13 and U14, which output voltages to gates of MOSFETs Q12 andQ13, respectively. Input to a drain of the MOSFETs Q12 and Q13 can comefrom the positive output of the first switching circuit via theconnection 186. The voltage V2 can also be provided through diodes D10and D11 (rated for 100 volts, 1 ampere) to the high-side gate driversU13 and U14 and also to charge capacitors C26 and C27 (e.g., 1.0microfarads, rated for 100 volts). When the high-side gate drivers U13and U14 are on, power can be provided to charge the capacitors C26 andC27 via the voltage V10 from the microcontroller U10 and circuitsincluding resistors R82-R85 and R86-R89, schottke diodes D12-D13 andD14-D15, zener diodes D16 and D17, capacitors C28 and C29, andtransistors Q14 and Q15.

The resistors R82, R86 and R88 can be about 330 ohms, the resistors R83,R85, R87, and R89 can be about 2.1 kilo-ohms, the resistor R84 can beabout 100 kilo-ohms, and the resistor R74 can be about 100 kilo-ohms.The capacitors C28 and C29 can be about 1.0 microfarads (rated for 100volts) and the zener diodes D16 and D17 can have a 15-volt breakdownvoltage. The identical circuits can also include resistors R90 and R91(e.g., both 10 kilo-ohms) and resistors R92 and R93 (15 ohms).

One of the two identical circuits can be switched on, while the other isswitched off, and vice versa, to provide forward or reverse polaritypower to the TE modules 26, allowing the TE management unit 10 to workin a cooling mode or a heating mode. The microcontroller U10 can controlsuch switching via the input voltage V9, as described below.

When the input V9 is high, current can flow through a resistor R94(e.g., 10 kilo-ohms), through the base to the emitter of transistor Q16to ground. This also can allow current flow from voltage source V1through a resistor R95 (e.g., 330 ohms), through the collector of thetransistor Q16 to ground. As a result, no current flows to the base oftransistor Q17 and it is not active. Because the transistor Q17 is notactive, no current is being pulled through the resistor R90 to thecollector of transistor Q17, and thus, no voltage is provided to turn onthe high-side gate driver U13. In addition, when the input V9 is high,current can flow through a resistor R96 (e.g., 330 ohms), through thebase to the emitter of transistor Q18 to ground. This pulls current fromvoltage V2 through the resistor R91, through the collector of thetransistor Q18 to ground, which then allows a voltage to be provided tothe high-side gate driver U14, thus turning it on. Therefore, when theinput V9 is high, the high-side gate driver U13 is off and the high-sidegate driver U14 is on.

When the input V9 is low, the transistor Q16 is not in active mode, andthus, current can flow from voltage source V1 through the resistor R95to turn on the transistor Q17, which in turn pulls current from voltagesource V2 through the resistor R90, allowing the high-side gate driverU13 to turn on. Also, when the input V9 is low, the transistor Q18 isnot in active mode, and thus, no voltage is provided to the high-sidegate driver U14. Therefore, when the input V9 is low, the high-side gatedriver U13 is on and the high-side gate driver U14 is off.

When the high-side gate driver U13 is on, voltage is applied to switchon the MOSFET Q12, which in turn provides voltage (from connection 186)supplied to the TE modules 26 at the connections 190 and 192. Also, whenthe high-side gate driver U13 is on, voltage from V2 is applied across athe resistor R90 and a resistor R97 (e.g., 10 kilo-ohms) to ground,which can switch on a MOSFET Q19. The active MOSFET Q19 provides areturn line from the TE modules 26 (at the connections 194 and 196) toground. While in this configuration, the TE management unit 10 can be ina cooling mode.

When the high-side gate driver U14 is on, voltage is applied to switchon the MOSFET Q13, which in turn provides voltage (from connection 186)supplied to the TE modules 26 at the connections 194 and 196. Also, whenthe high-side gate driver U14 is on, voltage from V2 is applied acrossthe resistor R91 and a resistor R98 (e.g., 10 kilo-ohms) to ground,which can switch on a MOSFET Q20. The active MOSFET Q20 then provides areturn line from the TE modules 26 (at the connections 190 and 192) toground. While in this configuration, the TE management unit 10 can be ina heating mode.

In some embodiments, the high-side gate drivers U11-U14 can each be PartNo. FAN7361, manufactured by Fairchild Semiconductor®, the transistorsQ5, Q6, Q8, Q9, Q15, Q16, Q17 and Q18 can be NPN transistors, such asPart No. MMBTH24, manufactured by Fairchild Semiconductor®, and theMOSFETs Q7, Q10, Q12, Q13, Q19, and Q20 can be Part No. IRF520NPBF,manufactured by International Rectifier.

The voltage V6 at connections 194 and 196 can be directed to the powermonitor circuit 54 for monitoring. In addition, a voltage V12 can bemonitored at the connections 190 and 192. The input voltage V7 (as shownin FIG. 11C) can be a variable voltage and can regulate a desired outputvoltage level to the TE modules 26 within about +/−1.0 Vdc. In someembodiments, the desired output voltage to the TE modules 26 can bebetween about 15 Vdc and about 60 Vdc, depending input voltage to the TEmanagement unit 10, with an output current up to about 13.5 amperes. Inone embodiments, the output voltage to the TE modules 26 can be betweenabout 0 Vdc and 3.0 Vdc less than the input voltage to the TE managementunit 10. As earlier discussed, the TE power circuit 164 is capable ofswitching the polarity of the output voltage to the TE modules 26 so theTE management unit 10 can operate in a cooling mode or a heating mode.

FIG. 11E illustrates the unit power circuit 166. The unit power circuit166 can provide power to the TE management unit 10, including the fanpower circuit 162, the TE power circuit 164, and the control circuit 39.The input voltage to the unit power circuit 166 can be supplied atconnections 198 and 200 (with return lines at connections 202 and 204).In some embodiments, the input voltage, such as from power input 203 inFIG. 12, can range from about 18 Vdc to about 60 Vdc, and an inputcurrent can be as high as about 20 amperes, direct current. The unitpower circuit 166 can be reverse-polarity protected with diode D18, suchas Part No. 30CPF12Pbf, a fast-soft recovery rectifier diode,manufactured by International Rectifier, among others. In otherembodiments, the input voltage can range from about 115 volts, alternatecurrent (Vac) to about 230 Vac, at about 50 Hertz to 60 Hertz. In suchembodiments, the unit power circuit 166 can include an additionaltransformer circuit (not shown) to produce a direct current voltageinput at the connections 198, 200, 202, and 204.

The unit power circuit 166 can have a series of filtering capacitorsC30-C33, followed by a voltage regulator U15, such as a high voltagestep down switching regulator (e.g., Part No. LM5008, manufactured byNational Semiconductor). The filtering capacitors C30, C31, C32, and C33can have a capacitance of 0.001 microfarads, 0.001 microfarads, 10microfarads, and 0.1 microfarads, respectively, and can all be rated for100 volts. The input voltage, after diode D18, can be connected to pin 8of the regulator U15. The input voltage can also be connected to pin 6,with a resistor R99 (e.g., 232 kilo-ohms) in between. Pins 3, 7, and 4can be connected to the return line, with a resistor R100 (e.g., 232kilo-ohms) between pin 3 and the return line, and a capacitor C34 (e.g.,0.1 microfarads, rated for 50 volts) between pin 7 and the return line.Pin 1 of the regulator U15, through inductor L3 (e.g., 470micro-Henries, rated for 0.79 amperes), outputs the voltage V2 for theTE management unit 10. A feedback voltage from a voltage dividerincluding the voltage V2 and resistors R101 (e.g., 10 kilo-ohms) andR102 (e.g., 2550 ohms) can be fed back to pin 5 of the regulator U15.Also, pin 2 of the regulator U15 can be connected to the output of pin1, with capacitor C35 (e.g., 0.01 microfarads) in between, followed bydiode D19, connected to ground.

The voltage V2 is connected to another voltage regulator U16 to producethe voltage V1 Transient protection capacitors C36-C39 can also bepresent before and after the regulator U16. The output of the regulatorU16, connected through a resistor R103 to ground, can be the voltage V1for the TE management unit 10. A fuse F1 can be provided before voltagesource V1 to prevent current overload. The fuse F1 can be a resettablefuse (i.e., a PTC). In some embodiments, the capacitors C36, C37, C38,and C39 can have a capacitance of 47 microfarads (rated for 25 volts),0.1 microfarads (rated for 50 volts), 10 microfarads (rated for 6.3volts), and 0.1 microfarads (rated for 50 volts), respectively. Thevoltage regulator U16 can be Part No. LD1117DT, manufactured by STMicroelectronics.

In addition, the input voltage, after diode D18, can be provided to thefan power circuit 162 and the TE power circuit 164, via the connection168. A bulk capacitor C40 (e.g., 4700 microfarads, rated for 80 volts)can be connected to the connection 168 to provide power to the fan powercircuit 162 and the TE power circuit 164 in case of any transients atthe input connections 198 and 200.

The wiring diagram of FIG. 12 illustrates the connections between thecontroller 38 and elements of the TE management unit 10. In someembodiments, the control circuit 39 and power circuit 41 can be housedin a junction box (not shown) remote from the TE management unit 10.FIG. 12 also shows a power input 203 for the controller 38. In addition,the control circuit 39 and the power circuit 41 can be custom printed ona printed circuit board (PCB) 205, which is then housed in the junctionbox. FIG. 13 illustrates a top side of the PCB 205 according to someembodiments of the invention.

FIGS. 14A-14G are flow charts of a control scheme according to oneembodiment of the invention for use with the TE management unit 10. Thecontrol scheme of FIGS. 14A-14G can be implemented via the control andpower circuits 39, 41 of the controller 38.

FIGS. 14A-14B illustrate a main routine for the TE management unit 10.After startup 206, the controller 38 proceeds to step 208, which caninclude flashing red and green LEDS (i.e., diodes D2 and D1 of the alarmcircuit 46) and toggling the alarm outputs for a first time period(e.g., four seconds). The controller 38 can then determine whether aloop counter is less than a preset integer (e.g., ten) at step 210. Ifthe loop counter is less than the preset integer, the controller 38 canproceed to step 212, which can include the controller 38 determining ifa fan feedback voltage (i.e., the voltage V3) is less than a fansetpoint voltage and if the PWM signal (i.e., the input voltage V8) isless than or equal to 80% duty cycle. The controller 38 can then eitherproceed to step 214 if the fan feedback voltage is less than the fansetpoint voltage and the PWM signal is less than or equal to 80%, or tostep 216 if the fan feedback voltage is more than the fan setpointvoltage or the PWM signal is less than or equal to 80%. At step 214, thecontroller 38 increases the PWM signal one step (i.e., one timinginterval). At step 216, the controller 38 decreases the PWM output onestep. Following either step 214 or step 216, the controller 38 restrictsthe PWM signal to between 0% to 80% duty cycle at step 218 (i.e., tokeep the duty cycle within a proper operating range). The controller 38then checks a fan over current comparator (i.e., the voltage V4) at step220. If the fan over current comparator is low, the controller 38 setsthe updated PWM signal (i.e., updates the input voltage V8) and resetsthe loop count to zero at step 222. If the fan over current comparatoris high, the controller 38 first proceeds to step 224 and sets the fanPWM signal to 0% duty cycle, then proceeds to step 222.

If, at step 210 the loop count is greater than the preset integer, thecontroller 38 proceeds to step 226 and calculates various temperaturesand voltages, checks the temperature sensors S1-S4 for any faults, andincrements the loop counter. Following either step 222 or 226, thecontroller 38 proceeds to step 228 (FIG. 14B) and determines if a secondtime period (e.g., 1 second) has passed since the last entry (i.e., thelast time the PWM signal was updated). If the second time period has notpassed, the controller 38 returns to step 210. If the second time periodhas passed, the controller 38 proceeds to step 230 and calculates thespeed of the fans 34, 36 (e.g., using the tachometer inputs). Followingstep 230, the controller 38 determines if a third time period (e.g., 2seconds) has passed since startup (step 206) by checking a startup timerat step 232. If not, the controller 38 proceeds to step 234 and adjuststhe enclosure fan PWM signal, toggles the polarity of the voltage outputto the TE modules 26 (i.e., via the voltage V9), and increments thestartup timer. If the third time period from step 232 has passed, thecontroller 38 proceeds to step 236 and determines if the time is betweenthe third time period from step 232 and a fourth time period (e.g., 4seconds after startup). If so, the controller 38 proceeds to step 238and adjusts the ambient fan PWM signal and increments the startup timer.If not, the controller 38 instead proceeds to step 240 and determines ifthe time after startup is past or is equal to the fourth time period. Ifso, the controller 38 proceeds to step 242 and adjusts the PWM signalfor both the enclosure fan 36 and the ambient fan 34. If not, thecontroller 38, at step 244, sets and clears any delayed alarm outputs,maps the alarm outputs to their respective alarms (i.e., at the alarmcircuit 46), and performs any miscellaneous “1-second updates,” such aschecking a door switch or a door alarm (via the tachometer circuit 44),then proceeds back to step 210 in FIG. 14A.

FIG. 14C illustrates a routine to set the fan PWM signals. Thecontroller 38 can modulate fan speeds (i.e., via the fan PWM signals) tomaintain a set temperature change across the TE modules 26 as measuredby the temperature sensors S1-S4 in the enclosure loop and the ambientloop. The following routine can be executed separately for the ambientfans 34 (i.e., using the ambient air loop temperatures) and theenclosure fans 36 (i.e., using the enclosure air loop temperatures).After startup 246 of the routine, the controller 38 determines if thefans 34, 36 are set in a “run” mode at step 248. If so, the controller38 calculates an air loop temperature change (e.g., the differencebetween enclosure inlet and outlet temperatures or the ambient inlet andoutlet temperatures) at step 250. Following step 250, the controller 38determines if the air loop temperature change is greater than a fanchange setpoint plus 3 (or some other set integer) at step 252. If so, aPWM step change value is set to 100 at step 254. If not, the controller38 determines if the air loop temperature change is greater than the fanchange setpoint plus 1 (or some other set integer) at step 256. If so,the PWM step change value is set to 25 at step 258. If not, thecontroller 38 determines if the air loop temperature change is greaterthan the fan change setpoint minus 1 (or some other set integer) at step260. If so, the PWM step change value is set to 5 at step 262. If not,the PWM step change value is set to 25 at step 264. Following any one ofsteps 254, 258, 262, or 264, the controller 38 proceeds to step 266 anddetermines if any alarms are active (e.g., airflow alarm, temperature orsensor failure alarm, power fault alarm, etc. described above). If analarm is active, the PWM step change value is set to 100 and the PWMstep change value is then subtracted from the PWM signals at step 268.Following step 268, the controller 38 restricts the enclosure fan PWMsignal between 75% and 100% and the ambient fan PWM signal between 25%to 100% at step 270, to keep the fans 34, 36 operating within desired,or operable, speed ranges. If, for example, the PWM signal is outsidethe ranges (such as 125%), the PWM signal is then set to its low or highlimit value (such as 100%, in this example). The controller 38 thenproceeds to step 272 and sets the updated PWM signal (i.e., updates theinput voltage V8) and tests the fan speeds for validity (e.g., using thetachometer circuit 44). Following step 272, the routine is completed274. In some embodiments, the target temperature change in the ambientair loop or the enclosure air loop can be about 7 degrees Celsius +/− 2degrees Celsius.

If, at step 266, there are no alarms active, the controller 38determines, at step 276, if the air loop temperature change is greaterthan the fan change setpoint. If not, the PWM step change value issubtracted from the PWM signals at step 278. If so, the PWM step changevalue is added to the PWM signals at step 280. Following either step 278or 280, the controller 38 proceeds to step 270 (described above).

If, at step 248, the controller 38 determines that the fans 34, 36 arenot in a “run” mode, the controller 38 determines if the fans 34, 36 arein an “off” mode at step 282. If the fans 34, 36 are in the off mode,the controller 38 proceeds to step 284 and sets the PWM signals to 0%,then proceeds to step 272. If the controller 38 determines at step 282that the fans are not in off mode, the controller 38 proceeds straightto step 272.

FIG. 14D illustrates a flowchart for an interrupt service routine (ISR)used by the controller 38 to calculate the voltage output to the TEmodules 26 (i.e., the “TE voltage output”). The controller 38 canmodulate the TE voltage output to maintain a desired heating or coolingtemperature set-point. The controller 38 can use a single temperaturecontrol zone as the input for TE voltage output control. For example,the controller 38 can use the inlet temperature of the enclosure airloop (e.g., as obtained from the temperature sensor S1) as an input tocontrol the TE voltage output. After startup 286 of the ISR, thecontroller 38 determines whether it is currently switching betweenheating and cooling modes at step 288. If so, the controller 38 sets a“TE reset” flag at step 290. If the controller 38 is not switchingmodes, or following step 290, the controller 38 determines if thetemperature in the enclosure inlet 11 is greater than a cool temperaturesetpoint at step 292 (e.g., via temperature sensor S1). If so, thecontroller 38 sets the TE management unit 10 to the cooling mode at step294, then proceeds to step 296 and determines if the air looptemperature change is greater than a maximum air loop temperaturechange. If so, the controller 38 sets the TE voltage output to 0 voltsat step 298. The controller 38 then confirms the TE voltage output iswithin a range of greater than or equal to 0 volts and less than orequal to 24 volts, and adjusts it accordingly if it is not, at step 300.Following step 300, the ISR is completed at step 302.

If, at step 292, the controller 38 determines that the enclosuretemperature is not greater than the cool temperature setpoint, thecontroller 38 proceeds to step 304 and determines if the enclosure inlettemperature is less than a warm temperature setpoint. If so, thecontroller 38 sets the TE management unit 10 to the heating mode at step306, then proceeds to step 296. If not, the controller 38 does nothingand proceeds to step 296 and determines if the air loop temperaturechange is greater than a maximum air loop temperature change.

If, at step 296, the controller 38 determines that the air looptemperature change is not greater than a maximum air loop temperaturechange, the controller 38 proceeds to step 308. At step 308, thecontroller 38 sets and records a setpoint error value as the differencebetween the enclosure temperature and the temperature setpoint, thensets a “sum of setpoint errors” value as the sum of the last 16 setpointerror values recorded. If the sum of setpoint errors value is above amaximum value, the controller 38 limits the sum of setpoint errors valueto the maximum value. The controller 38 then sets a voltage adjust valueas the product of a constant Kp and the setpoint error value plus aproduct of another constant Ki and the sum of setpoint errors value. Thecontroller 38 then proceeds to step 310 and determines if the TEmanagement unit 10 is in cooling mode. If so, the controller 38 proceedsto step 312 and adds the voltage adjust value to the current TE voltageoutput value. If not, the controller 38 proceeds to step 314 andsubtracts the voltage adjust value from the current TE voltage outputvalue. Following either step 312 or step 314, the controller 38determines if an enclosure temperature alarm (e.g., the temperature orsensor failure alarm or the airflow alarm) is active at step 316. If so,the controller 38 sets the TE voltage output to 18 Vdc at step 318. Ifthere is no enclosure temperature alarm active at step 316, or followingstep 318, the controller 38 determines if a fan alarm (e.g., the airflowalarm or the power fault alarm) is active at step 320. If so, thecontroller 38 sets the TE voltage output to 0 volts at step 322. Ifthere is no fan alarm active at step 320, or following step 322, thecontroller 38 proceeds to step 300 and confirms the TE voltage output iswithin a range of greater than or equal to 0 volts and less than orequal to 24 volts, and adjusts the TE voltage output accordingly if itis not. Following step 300, the ISR is completed at step 302. Thetemperature set points in steps 292 and 304 can be factory-set oradjusted through a programming interface (e.g., the programminginterface 52), display board, or other user interface by a user. Also,in some embodiments, if the TE management unit 10 is between temperatureset-points upon startup, the controller 38 can default to heating mode.

FIG. 14E illustrates a flowchart for an ISR used by the controller 38 tocalculate the TE module PWM output (i.e., the voltage V7). After startup324 of the ISR, the controller 38 determines whether the TE voltagefeedback value (i.e., the feedback voltage V4) is less than a TE voltagesetpoint at step 326. If so, the TE PWM output is increased one step atstep 328. If not, the PWM output is decreased one step at step 330.Following either step 320 or 330, the controller 38 determines if the TEPWM output is set to greater than 100% duty cycle at step 332. If so,the controller 38 limits the TE PWM output to 100% at step 334. If theTE PWM output is not greater than 100% at step 332, or following step334, the controller 38 determines if the TE PWM output is either lessthan 0% or the TE over current comparator's output is high at step 336(e.g., from the voltage V6 or the voltage V12). If either is true, theTE PWM output is set to 0% at step 338. If one or both are not true atstep 336, or following step 338, the controller 38 sets the updated TEmodule PWM output signal (i.e., updates the input voltage V7) and resetsthe ISR timer at step 340. Following step 340, the ISR is completed atstep 342.

FIG. 14F illustrates a flowchart for a fan over-current ISR. Afterstartup 334 of the ISR, the controller 38 determines, on the rising edgeof a clock signal (i.e., as a rising edge interrupt), whether anamplified voltage on a fan current sense resister (i.e., the voltage V5from resistor R68) is greater than a fan current limit (step 336). Thefan current limit can be set by a digital-to-analog converter of themicrocontroller U10. If the voltage on the fan current sense resister isgreater than the fan current limit at step 336, the controller 38proceeds to step 338 and stops the fans 34, 36. In particular, in step338, the controller 38 sets the PWM signal value (i.e., the voltage V8)to 0% duty cycle, updates the PWM signal, and resets the ISR. If thevoltage on the fan current sense resister is not greater than the fancurrent limit at step 336, or following step 338, the controller 38determines on the falling edge of a clock signal (i.e., as a fallingedge interrupt), whether the amplified voltage on the fan current senseresister is less than the fan current limit (step 340). If so, thecontroller 38 resets the ISR at step 342. If not, or following step 342,the ISR is completed at step 344.

FIG. 14G illustrates a flowchart for a TE over-current ISR. Afterstartup 346 of the ISR, the controller 38 determines, on the rising edgeof a clock signal (i.e., as a rising edge interrupt), whether anamplified voltage on a TE current sense resister is greater than a TEcurrent limit (step 348). The TE current limit can be set by adigital-to-analog converter of the microcontroller U10. If the voltageon the TE current sense resister is greater than the TE current limit atstep 348, the controller 38 proceeds to step 350 and stops providingpower to the TE modules 26. In particular, in step 350, the controller38 sets the TE module PWM output to 0%, updates the TE module PWMoutput, and resets the ISR. If the voltage on the TE current senseresister is not greater than the TE current limit at step 348, orfollowing step 350, the controller 38 determines on the falling edge ofa clock signal (i.e., as a falling edge interrupt), whether theamplified voltage on the TE current sense resister is less than the TEcurrent limit (step 352). If so, the controller 38 resets the ISR atstep 354. If not, or following step 354, the ISR is completed at step356.

In some embodiments, as shown in FIGS. 15A and 15B, the TE managementunit 10 can incorporate a separator printed circuit board (PCB) 358, inplace of the panel 32 (shown in FIGS. 1A-1B). The separator PCB 358 canextend the physical length and width of the TE management unit 10. Theseparator PCB 358 can be used to integrate several functions of thecontroller 38, as well as also separate the cold and warm thermalcircuits of the TE modules 26, as also shown in FIG. 16. Further, theseparator PCB 358 can separate the enclosure side 16 from the ambientside 18 of the TE management unit 10.

The separator PCB 358 can be custom-made, and thus, can be populatedwith different electronic circuits that perform several differentfunctions, such as control, regulation, monitoring, etc. of the TEmanagement unit 10. FIG. 17 illustrates an enclosure side 357 of theseparator PCB 358, and FIG. 18 illustrates an ambient side 359 of theseparator PCB 358 according to one embodiment of the invention. If theTE management unit 10 is mainly used for cooling the enclosure, theseparator PCB 358 can keep delicate electronic circuits on the enclosureside 357 (e.g., the cool side) to provide higher reliability.

The separator PCB 358 can provide some or all of the electrical andelectronic connections for the controller 38 and the elements of the TEmanagement unit 10. For example, the separator PCB 358 can include someor all elements necessary to perform the same functions of the controlcircuit 39 and power circuit 41 described above (i.e., at least thefunctions described in flow charts 13A-13G). Thus, the separator PCB 358can allow for the TE modules 26 as well as other components of the TEmanagement unit 10 to reliably connect and interconnect on the traces ofthe PCB, rather than using separate circuitry and connectors. Theseparator PCB 358 can integrate circuitry without the need, or withminimal need, for external housings or junction boxes.

FIG. 19A illustrates a schematic of a power circuit 360, according toanother embodiment of the invention, that can be implemented on theseparator PCB 358. An accompanying control circuit 361 (illustrated inFIGS. 20A-20G) can be implemented on another PCB (not shown) remote fromand connected to the separator PCB 358. In other embodiments, both thepower circuit 360 and the control circuit 361 (or the power circuit 41and the control circuit 39) can be implemented on the separator PCB 358.As shown in FIG. 19A, the power circuit 360 can include a main powerinput 362 (further illustrated in FIG. 19B), a low voltage supply 364(further illustrated in FIG. 19C), a high voltage supply 366 (furtherillustrated in FIG. 19D), a bulk power regulator 368 (furtherillustrated in FIG. 19E), an H-bridge 370 (further illustrated in FIG.19F), fan power outputs 372 (further illustrated in FIG. 19G), and TEstack connections 374 (further illustrated in FIG. 19H). Dotted linesbetween the elements of the power circuit 360 illustrate virtualconnections where voltage inputs are referenced to and from.

FIG. 19B illustrates the main power input circuit 362. The input voltageto the TE management unit 10 can be supplied at connections 198 and 200(with return lines at connections 202 and 204). Following filteringcapacitors C41 and C42 (e.g., 2000 microfarads, rated for 80 volts, and1.0 microfarads, rated for 100 volts, respectively) can be a referencepower voltage V13. The voltage V13 can be provided to the low voltagesupply 364 and the high voltage supply 366. In addition, the main powerinput 362 can include an earth ground reference via connections 376 and378. In some embodiments, the input voltage, such as from power input203 in FIG. 12, can range from about 18 Vdc to about 60 Vdc, and aninput current can be as high as about 20 amperes, direct current. Inother embodiments, the input voltage can range from about 115 volts,alternate current (Vac) to about 230 Vac, at about 50 Hertz to 60 Hertz.In such embodiments, the main power input circuit 362 can include anadditional transformer circuit (not shown) to produce a direct currentvoltage input at the connections 198, 200, 202, and 204.

FIG. 19C illustrates the low voltage supply circuit 364. The low voltagesupply 364 regulates the reference power voltage V13 down to a lowsupply voltage V14 (e.g., 3.3 volts) to be used by the H-bridge 370 andthe control circuit 361. The low voltage supply 364 can have a series offiltering capacitors C43-C44, followed by a voltage regulator U17, suchas a high voltage step down switching regulator (e.g., Part No. LM5008,manufactured by National Semiconductor). The filtering capacitors C43and C44 can have a capacitance of 0.1 microfarads and 1.0 microfarads,respectively, and can both be rated for 100 volts. The reference powervoltage V13 can be connected to pin 8 of the regulator U17. The voltageV13 can also be connected to pin 6, with a resistor R104 (e.g., 232kilo-ohms) in between. Pins 3, 7, and 4 can be connected to ground, witha resistor R105 (e.g., 232 kilo-ohms) between pin 3 and ground, and acapacitor C45 (e.g., 0.1 microfarads) between pin 7 and ground. Pin 1 ofthe regulator U17, through inductor L4 (e.g., 470 micro-Henries, ratedfor 0.79 amperes), outputs the voltage V14 for the TE management unit10. A feedback voltage from a voltage divider including the voltage V14and resistors R106 (e.g., 1 kilo-ohm) and R107 (e.g., 3.46 kilo-ohms)can be fed back to pin 5 of the regulator U17. Also, pin 2 of theregulator U17 can be connected to the output of pin 1, with capacitorC46 (e.g., 0.1 microfarads, rated for 100 volts) in between, followed bydiode D20, connected to ground. The low voltage supply 364 can furtherinclude capacitors C47 (10 microfarads, rated for 16 volts) and C48 (0.1microfarads, rated for 50 volts) for transient protection.

FIG. 19D illustrates the high voltage supply circuit 366. The highvoltage supply 366 regulates the reference power voltage V13 down to ahigh supply voltage V15 (e.g., 12 volts) to be used by the bulk powerregulator 368, the H-bridge 370, and the control circuit 361. The highvoltage supply 366 can have a series of filtering capacitors C49-050,followed by a voltage regulator U18, such as a high voltage step downswitching regulator (e.g., Part No. LM5008, manufactured by NationalSemiconductor). The filtering capacitors C49 and C50 can have acapacitance of 0.1 microfarads and 1.0 microfarads, respectively, andcan both be rated for 100 volts. The reference power voltage V13 can beconnected to pin 8 of the regulator U18. The voltage V13 can also beconnected to pin 6, with a resistor R108 (e.g., 232 kilo-ohms) inbetween. Pins 3, 7, and 4 can be connected to ground, with a resistorR109 (e.g., 232 kilo-ohms) between pin 3 and ground, and a capacitor C51(e.g., 0.1 microfarads) between pin 7 and ground. Pin 1 of the regulatorU17, through inductor L5 (e.g., 470 micro-Henries, rated for 0.79amperes), outputs the voltage V15 for the TE management unit 10. Afeedback voltage from a voltage divider including the voltage V15 andresistors R110 (e.g., 13.7 ohms) and R111 (e.g., 2.4 ohms) can be fedback to pin 5 of the regulator U18. Also, pin 2 of the regulator U18 canbe connected to the output of pin 1, with capacitor C52 (e.g., 0.1microfarads, rated for 100 volts) in between, followed by diode D21,connected to ground. In addition, a resistor R112 (e.g., 33 kilo-ohms)can be connected between pins 1 and 5. The high voltage supply 366 canfurther include capacitors C53 (5600 picofarads, rated for 50 volts),C54 (10 microfarads, rated for 16 volts), and C55 (0.1 microfarads,rated for 50 volts) for transient protection. The high voltage V15 canbe connected to the bulk power regulator 368 via a connection 380, withthree diodes D22, D23, and D24 (all rated for 100 volts and 1 ampere) inbetween for reverse-voltage protection.

FIG. 19E illustrates the bulk power regulator circuit 368. The bulkpower regulator circuit 368 regulates the reference power voltage V13down to a voltage V16 for use with the H-bridge 370. The bulk powerregulator circuit 368 can include a synchronous buck controller U19 suchas Part No. LM5116, manufactured by National Semiconductor. Pin 1 of thecontroller U19 can be connected to the reference power voltage V13. Pin1 of the controller U19 can also be connected to ground with a capacitorC56 (e.g., 0.1 microfarads, rated for 100 volts) in between. Pin 2 ofthe controller U19 can be connected to a voltage divider between thevoltage V13 and ground, including two resistors R113 (e.g., 232kilo-ohms) and R114 (e.g., 20 kilo-ohms). In addition, a diode D25(rated for 100 volts, 1 ampere) separates the input at pin 2 and V13,and a capacitor C57 (e.g., 1.0 microfarads) separates the input at pin 2and ground. Pin 3 of the buck controller U19 is connected to ground witha resistor R115 (e.g., 12.4 kilo-ohms) in between. Pin 4 of thecontroller U19 can either be connected to voltage V13 via the resistorR116 (e.g., 750 kilo-ohms) or connected to ground via a switch SW1. Pin5 of the controller U19 can be connected to ground with a capacitor C58(e.g., 1 kilo-picofarad) in between. Pin 5 of the controller U19 canalso be connected to pin 16 via resistor R117 (e.g., 100 kilo-ohms),which is then connected to ground with a capacitor C59 (e.g., 1.0microfarads) in between.

Pins 6, 11, 13, 14, and 21 of the controller U19 can be connected toground. Pins 6, 14, and 21 can also be connected to the voltage V13 withthe capacitor C56 in between. Pin 7 of the controller U19 can beconnected to ground with a capacitor C60 (e.g., 0.01 microfarads) inbetween. Pins 8 and 9 of the controller U19 can be connected to theoutput of the controller U19 at pin 10. For example, pin 8 can be afeedback input. A compensation loop connected between pins 8 and 9 caninclude a resistor R118 (e.g., 27.4 kilo-ohms) and capacitors C61 (e.g.,0.01 microfarads) and C62 (e.g., 1 kilopicofarad). The compensation loopcan be connected to pin 10 via feedback resistors R119 (e.g., 16.4kilo-ohms), R120 (e.g., 650 ohms), R121 (e.g., 180 ohms), and high powerjumper J3 in connection with ground.

The bulk power regulator 368 further includes a pair of MOSFETs Q21 andQ22. The source of MOSFET Q21 and the drain of MOSFET Q22 can beconnected. Pins 19 and 15 of the controller U19 can be connected to thegates of the MOSFETs Q21 and Q22, respectively. The drain of MOSFET Q21can be connected to the voltage V13. The source of MOSFET Q22 and pin 12of the buck controller U19 can be connected to ground with a resistorR122 (e.g., 0.005 ohms, rated for 1 watt) in between. Pins 16, 18, and20 of the controller U19 can be connected between the source of MOSFETQ21 and the drain of MOSFET Q22 via resistor R123, a diode D26, and acapacitor C63. Also connected between the source of MOSFET Q21 and thedrain of MOSFET Q22 can be the output from pin 10 of the controller U19with an inductor L6 in between, followed by an output capacitor bankC64, leading to the regulated, direct current voltage V16. The outputcapacitor bank C64 can include ten 10-microfarad capacitors, all ratedfor 35 volts, and can be followed by another capacitor C65 (e.g., 680microfarads, rated for 35 volts). The bulk power regulator 368 canfurther include an input capacitor bank, including capacitors C66, C67,C68, and C69 (each 2.2 microfarads, rated for 100 volts) connected tothe voltage V13. In addition, the voltage V15, from the connection 380can be connected to the input pin 17. The input pin 17 can further beconnected to ground through a capacitor C70 for transient filtering.

FIG. 19F illustrates the H-bridge 370. The H-bridge 370 includes twoidentical circuits. The voltage V15 is provided to high-side gatedrivers U20 and U21, which can provide voltage to gates of MOSFETs Q23and Q24. Input to a drain of each MOSFET Q23 and Q24 can come from thevoltage V16. The voltage V15 can also be provided through diodes D27 andD28 (rated for 100 volts, 1 ampere) to the high-side gate drivers U20and U21 and also to charge capacitors C71 and C72 (e.g., 1.0microfarads, rated for 100 volts), respectively. When one of thehigh-side gate drivers U20 and U21 is on, power can be provided tocharge the respective capacitor C71 or C72 via the voltage V17 andcircuits including resistors R124-R126 and R127-R129, schottke diodesD29-D30 and D31-D32, capacitors C73 and C74, and transistors Q25 andQ26.

The resistors R124 and R127 can be about 2.0 kilo-ohms, the resistorsR125 and R128 can be about 1 kilo-ohm, and the resistors R126 and R129can be about 470 ohms. The capacitors C73 and C74 can be about 1.0microfarads (rated for 100 volts). The identical circuits can alsoinclude resistors R130 and R131 (e.g., each 10 kilo-ohms), resistorsR132 and R133 (e.g., each 15 ohms), and capacitors C75 and C76 (e.g.,each 10 microfarads, rated for 16 volts).

One of the two identical circuits can be switched on, while the other isswitched off, and vice versa, to provide forward or reverse polaritypower to the TE modules 26, allowing the TE management unit 10 to workin a cooling mode or a heating mode. The control circuit 361 can controlsuch switching via the input voltages V18 and V19, as described below.

When the voltage V18 is high, current can flow through a resistor R134(e.g., 470 ohms), through the base to the emitter of transistor Q27 toground. This pulls current from voltage V15 through the resistor R131,through the collector of the transistor Q27 to ground, which then allowsa voltage to be provided to the high-side gate driver U21, thus turningit on. In addition, when voltage V18 is high, voltage V19 can be low.When voltage V19 is low, no current travels to the base of transistorQ28 and it is not active. Because the transistor Q28 is not active, nocurrent is being pulled through the resistor R128 to the collector oftransistor Q28, and thus, no voltage is provided to turn on thehigh-side gate driver U20. Therefore, when the voltage V18 is high andthe voltage V19 is low, the high-side gate driver U20 is off and thehigh-side gate driver U21 is on. Also, the voltage V14 can be providedat the output of voltage V18 with a resistor R135 (e.g., 232 kilo-ohms)in between.

When the voltage V18 is low, the transistor Q27 is not in active mode,and thus, no voltage is provided to the high-side gate driver U21. Also,when the voltage V18 is low, the voltage V19 is high, and current isallowed to flow through the transistor Q28, which in turn pulls currentfrom voltage source V15 through the resistor R130, allowing thehigh-side gate driver U20 to turn on. Therefore, when the voltage V18 islow and the voltage V19 is high, the high-side gate driver U20 is on andthe high-side gate driver U21 is off.

When the high-side gate driver U20 is on, voltage is applied to switchon the MOSFET Q23, which in turn provides voltage V16 supplied to the TEmodules 26 (i.e., at voltage V20). Also, when the high-side gate driverU20 is on, voltage from V15 is applied across a the resistor R130 and aresistor R136 (e.g., 232 kilo-ohms) to ground, which can switch on aMOSFET Q29. The active MOSFET Q29 provides a return line from the TEmodules 26 (i.e., voltage V21) to ground. While in this configuration,the TE management unit 10 can be in a cooling mode. Also, the voltageV14 can be provided at the output of voltage V19 with a resistor R137(e.g., 232 kilo-ohms) in between.

When the high-side gate driver U21 is on, voltage is applied to switchon the MOSFET Q24, which in turn provides voltage V16 supplied to the TEmodules 26 (i.e., at voltage V21). Also, when the high-side gate driverU21 is on, voltage from V15 is applied across the resistor R129 and aresistor R138 (e.g., 232 kilo-ohms) to ground, which can switch on aMOSFET Q30. The active MOSFET Q30 then provides a return line from theTE modules 26 (i.e., voltage V20) to ground. While in thisconfiguration, the TE management unit 10 can be in a heating mode.

Both the voltages V18 and V19 can be pulse-width modulated by thecontroller 38. In some embodiments, the high-side gate drivers U20-U21can each be Part No. FAN7361, manufactured by Fairchild Semiconductor®,the transistors Q25, Q26, Q27 and Q28 can be NPN transistors, such asPart No. MMBTH24, manufactured by Fairchild Semiconductor®, and theMOSFETs Q23, Q24, Q29, and Q30 can be Part No. IRF520NPBF, manufacturedby International Rectifier. In addition, the voltage V16 and ground caneach be connected to the earth ground reference via capacitors C77 andC78.

FIG. 19G illustrates the fan power outputs 372. Input power to four fans34, 36, via connections 382, 384, 386, and 388 can come from the voltageV16 from the bulk power circuit 368. Return voltage from the fans 34,36, via connection 390, 392, 394, and 396 can lead to ground.

FIG. 19H illustrates the TE stack connections 374 according to oneembodiment of the invention. Power to the TE stack can come fromvoltages V20 and V21 from the H-bridge 370. As previously described,power to the TE modules 26 can be forward or reverse polarity dependingon whether the TE management unit 10 is in cooling mode or heating mode.In the illustrated embodiment, the TE stack (including TE modulesTE1-TE12) is arranged in four strings, with each string including threemodules connected in parallel.

FIG. 20A illustrates a schematic of the control circuit 361, accordingto one embodiment of the invention. The control circuit 361 can beimplemented on another PCB (not shown) remote from and connected to theseparator PCB 358. In other embodiments, both the power circuit 360 andthe control circuit 361 (or the power circuit 41 and the control circuit39) can be implemented on the separator PCB 358. As shown in FIG. 20A,the control circuit 361 can include a temperature sensor circuit 398(further illustrated in FIG. 20B), a fan speed control circuit 400(further illustrated in FIG. 20C), a tachometer circuit 402 (furtherillustrated in FIG. 20D), an alarm circuit 404 (further illustrated inFIG. 20E), a memory/external ports circuit 406 (further illustrated inFIG. 20F), a programming interface 408 (further illustrated in FIG.20G), a solid state (SS) relay drive 409 (further illustrated in FIG.20H), and a microcontroller circuit 410 (further illustrated in FIG.20I). In one embodiment, these components can be connected as shown byconnections in FIG. 20A and described below. Dotted lines between theelements of the control circuit 361 illustrate virtual connections wherevoltage inputs are referenced to and from.

FIG. 20B illustrates the temperature sensor circuit 398 of the controlcircuit 361. The temperature sensor circuit 398 can include fourtemperature sensors S5-S8. The temperature sensors S5-S8 can be similarto temperature sensors S1-S4, described above. Each temperature sensorS5-S8 can have an accompanying sensor circuit including three resistorsand one capacitor: Resistors R139-R141 and capacitor C79 for sensor S5;resistors R142-R144 and capacitor C80 for sensor S6; resistors R145-R147and capacitor C81 for sensor S7; and resistors R148-R150 and capacitorC82 for sensor S8. In some embodiments, resistors R139, R142, R145, andR148 can be about 232 kilo-ohms with a 1% tolerance, resistors R140,R143, R146, and R149 can be about 1 kilo-ohm and resistors R141, R144,R147, and R150 can be about 10 kilo-ohms. In addition, capacitorsC79-C82 can have a capacitance of about 0.1 microfarads. Eachaccompanying sensor circuit can also include an input voltage, V14(e.g., 3.3. volts).

The first sensor circuit, including sensor 55, can be routed to themicrocontroller circuit 410 via a connection 412. The second sensorcircuit, including sensor S6, can be routed to the microcontrollercircuit 410 via a connection 414. The third sensor circuit, includingsensor S7, can be routed to the microcontroller circuit 410 via aconnection 416. The fourth sensor circuit, including sensor S8, can berouted to the microcontroller circuit 410 via a connection 418. Inaddition, an external sensor circuit, including resistors R151 (e.g., 10kilo-ohms) and R152 (e.g., 3.46 kilo-ohms), and capacitor C83 (e.g., 01microfarad) can be connected to the microcontroller circuit 410 via aconnection 420. The external sensor circuit can accompany an externalsensor S9, which may be, for example, a door switch or a smoke detector.The external sensor S9 can receive power from the voltage V15.

One of the temperature sensors (S5, for example) can be positioned atthe enclosure inlet 11 and another temperature sensor (S6, for example)can be positioned at the enclosure outlet 13. A third temperature sensor(S7, for example) can be positioned at the ambient inlet 15 and a fourthtemperature sensor (S8, for example) can be positioned at the ambientoutlet 17. Therefore, temperatures can be sensed at both the inlets andoutlets of the enclosure air loop and the ambient air loop. Thetemperature sensors S5-S8 can have a temperature accuracy of about +/− 2degrees Celsius.

FIG. 20C illustrates the fan speed control circuit 400 of the controlcircuit 361. The fan speed control circuit 400 can operate servomotorsfor each fan 34, 36. In some embodiments, PWM speed control can be usedto operate the servomotors (i.e., via the fan speed control circuit400), and open collector tachometers can be used for feedback (i.e., viathe tachometer circuit 402, described below), allowing full closed-loopdigital control for the fans 34, 36. The fan speed control circuit 400can connect to PWM inputs for each fan 34, 36. For example, a connection422 can lead to a PWM input for the first ambient fan 34, a connection424 can lead to a PWM input for the second ambient fan 34, a connection426 can lead to a PWM input for the first enclosure fan 36, and aconnection 428 can lead to a PWM input for the second enclosure fan 36.

The controller 38 can independently speed control each of the four fans34, 36 separately. To speed control the first ambient fan 34 (viaconnection 422), a PWM signal from the microcontroller circuit 410 istransmitted to a resistor R153 via a connection 430 and can switch onand off a transistor Q31. The base of the transistor Q31 can beconnected to the resistor R153 and the emitter of the transistor Q31 canbe connected to ground. When the signal from connection 430 applies asubstantial cut-in voltage across the base-emitter junction, thetransistor Q31 becomes active and allows current flow from the collectorto the emitter. This current is conducted from the voltage source V15,through resistors R154 and R155, and through the collector and theemitter to ground. The connection 422 is connected between the resistorsR154 and R155 to provide the PWM input to the first ambient fan 34 whenthe transistor Q31 is on. This method and configuration is also used tospeed control the second ambient fan 34, and the first and secondenclosure fans 36 as well, via signals through connections 432, 434, and436, respectively, from the microcontroller circuit 410, as illustratedin FIG. 20C. The resistor R153, and resistors R156, R159, and R162, canbe about 100 ohms. The resistor R154, and resistors R157, R160, andR163, can be about 100 kilo-ohms. The resistor R155, and resistors R158,R161, and R164, can be about 100 ohms. The transistor Q31, andtransistors Q32, Q33, and Q34, can be simple NPN, BJT transistors, suchas Part No. 2N222, manufactured by Fairchild Semiconductors®, amongothers.

FIG. 20D illustrates the tachometer circuit 402 of the control circuit361. The controller 38 can receive outputs from open collectortachometers (not shown) in connection with the fans 34, 36 to monitorfan speed, as described above. A connection 438 can be connected to thetachometer output of the first ambient fan 34, a connection 440 can beconnected to the tachometer output of the second ambient fan 34, aconnection 442 can be connected to the tachometer output of the firstenclosure fan 36, and a connection 444 can be connected to thetachometer output of the second enclosure fan 36. Each tachometer outputconnection 438, 440, 442, 444 can have an accompanying circuit includingtwo resistors and one capacitor leading to a multiplexer U22: ResistorsR165-R166 and capacitor C84 for the connection 438, leading to pin 4 ofthe multiplexer U22; resistors R167-R168 and capacitor C85 for theconnection 440, leading to pin 3 of the multiplexer U22; resistorsR169-R170 and capacitor C86 for the connection 442, leading to pin 2 ofthe multiplexer U22; and resistors R171-R172 and capacitor C87 for theconnection 444, leading to pin 1 of the multiplexer U22. The resistors,R165, R167, R169, and R171 can be about 100 kilo-ohms. The resistorsR166, R168, R170, and R172 can be about 1 kilo-ohms. The capacitorsC84-C87 can be about 0.01 microfarads.

The multiplexer U22 can be an 8-input multiplexer, such as Part No.74HC151, manufactured by Philips Semiconductors. Pins 1-4, which can becoupled to connections 438, 440, 442, and 444 can be multiplexer inputsof U2. Pins 12-15 can also be multiplexer inputs and can receive outputsfrom various override devices (not shown), such as smoke detectors, doorswitches, etc., which the controller 38 can monitor. When none of pins12-15 are connected to override devices, as illustrated in FIG. 20D, thepins 12-15 can be connected to ground. In addition, select inputs topins 9-11 of U22 can be routed from the alarm circuit 404 viaconnections 446, 448, and 450, respectively. The output V22 of themultiplexer U22 (from pin 5) can be routed to the microcontrollercircuit 410.

FIG. 20E illustrates the alarm circuit 404 of the control circuit 361.The alarm circuit 404 can include four red LEDs and four green LEDs (notshown) as visual indicators for alarm outputs. For example, a firstalarm output can be connected to a red LED via connection 452 and agreen LED via connection 454, a second alarm output can be connected toa red LED via connection 456 and a green LED via connection 458, a thirdalarm output can be connected to a red LED via connection 460 and agreen LED via connection 462, and a fourth alarm output can be connectedto a red LED via connection 464 and a green LED via connection 466.Alarm outputs can be controlled via a latch U23.

As shown in FIG. 20E, the first alarm output is connected to the latchU23 at pin 4. The red LED of the first alarm output, at connection 452,is connected directly to the output of pin 4, while the green LED, atconnection 454, is connected via an inverter G1 and a resistor R173.Thus, when the output at pin 4 is low, the red LED is off and the greenLED is on, which can indicate there is no fault present. However, whenthe output at pin 4 is high, the red LED is on and the green LED is off,which can indicate that there is a fault in the TE management unit 10.Similarly, for the second alarm output, the red LED is connected to thelatch U23 at pin 5 and the green LED, at connection 458, is connected topin 5 via an inverter G2 and a resistor R174; for the third alarmoutput, the red LED is connected to the latch U23 at pin 6 and the greenLED, at connection 462, is connected to pin 6 via an inverter G3 and aresistor R175; and for the fourth alarm output, the red LED is connectedto the latch U23 at pin 7 and the green LED, at connection 466, isconnected to pin 7 via an inverter G4 and a resistor R176. The resistorsR173-176 each can have a resistance of about 470 ohms.

The latch U23 can also output signals to communicate alarm outputs witha remote device (not shown). For example, pin 9 can be connected to theremote device at connections 468, 470, and 472 via the circuit includingresistor R177 (e.g., 470 ohms), diode D33, transistor Q35, referencevoltage V15 and signal relay U24. The signal relay U24 can have bothnormally open and normally closed contacts, allowing alarm outputs to becommunicated to the remote device in a zero potential circuit.

The latch U23 can be an 8-bit addressable latch, such as Part No.74HC259, manufactured by Philips Semiconductors. Address inputs to pins1, 2, and 3 can be from input voltages V23, V24, and V25, respectively,from the microcontroller circuit 410. An enable input to pin 14 can befrom input voltage V26 from the microcontroller circuit 410. Pin 15 canbe a conditional reset input, which is active when low, and can beconnected to voltage V15. Pin 13 can receive input data from themicrocontroller circuit 410 via an input voltage V27. The outputvoltages at pins 10, 11, and 12 (voltages V28, V29 and V30,respectively) can be routed to the tachometer circuit 402 via theconnections 446, 448, and 450.

FIG. 20F illustrates the memory/external ports circuit 406 of thecontrol circuit 361. The memory/external ports circuit 406 can include aserial port at connections 474, 476, 478 and 480, which can allow RS-232communication between the microcontroller circuit 410 and an outsidesource (e.g., an external computer) for automated test functions, datalogging, etc. The connection 476 can receive signals from themicrocontroller circuit 410 via a connection 482 through resistor R180(e.g., 1 kilo-ohm) and the connection 478 can transmit signals to themicrocontroller circuit 410 via a connection 484 through resistor R181(e.g., 1 kilo-ohm). The connection 474 can supply power to the outsidesource, via the voltage V14, and the connection 480 can be groundconnection for the outside source. The outside source can command thecontroller 38 via the serial port to run in a manual mode and beginautomated testing. The outside source can further command the controller38 back into normal mode to continue normal operation after, or during,testing. For example, the outside source can manually override controltemperatures to force the TE management unit 10 to run in a certain teststate. The outside source can send a request to receive all controllerdata during or after the test. The controller data from past operationscan be collected and/or data can be collected in near real-time. Thecontroller data can be processed by the outside source to determine theresults of the test. If, while connected to the outside source and acommand is not received for a time period, such as 15 seconds, thecontroller 38 can revert back to normal mode.

The memory/external ports circuit 406 can also include a memory chip U25and connection port J4. The memory chip U25 can be a SEEPROM (serialEEPROM) chip. The connection port J4 can be used to connect an externaldevice, such as a display board. “I2C” communications can be used forcommunication between the microcontroller circuit 410, the memory chipU25, and the connection port J4 via connections 486 and 488. Forexample, I2C communications can be used with the memory chip U25 forloading and storing controller runtime variables and logging faults. Insome embodiments, connection 488 can be the data line and connection 486can be the clock line. Also, resistors R178 and R179 (both about 1kilo-ohm) can be included in the memory/external ports circuit 406,connecting voltage V14 to connections 486 and 488, respectively. Inaddition, when not connected to an external device, the connection portJ4 can be connected to voltages V14 and V15 with filtering capacitorsC88-C93. The capacitors C88, C89, C91, and C92 each can have acapacitance of about 1 microfarad and the capacitors C90 and C93 eachcan have a capacitance of about 10 microfarads, rated for 16 volts.

The memory/external ports circuit 406 can further include a connectionport (including connections 490, 492, 494, and 496) for remote devices,such as slave units. For example, input to the remote unit, at theconnection 494, can come from the microcontroller circuit 410 via aconnection 498. Output from the remote unit, at the connection 492, canbe routed to the microcontroller circuit 410 via a connection 500. Apull-up voltage, such as voltage V14 can be connected to the remote unitat the connection 490, and a return from the remote unit, at theconnection 496, can lead to ground. The connection port can includeresistors R182 (e.g., 100 kilo-ohms), R183 (e.g., 1 kilo-ohm), R184(e.g., 1 kilo-ohm), and capacitor C94 (e.g., 0.1 microfarads).

FIG. 20G illustrates the programming interface 408 of the controlcircuit 361. The programming interface 408 can include a reprogrammingport J5 to allow reprogramming of a microcontroller U26 (illustrated inFIG. 20I) within the microcontroller circuit 410 once the TE managementunit 10 is already installed. Five pins of the reprogramming port J5 canbe connected to the microcontroller circuit 410 via connections 502,504, 506, 508, and 510, three pins be connection to ground, and two pinscan be connected to voltage source V14. One of the two pins connected tothe voltage source V14 is connected via a resistor R185 (e.g., about47.5 kilo-ohms).

FIG. 20H illustrates the SS relay drive 409 of the control circuit 361.The SS relay drive 409 can power external circuits (not shown) with asolid state relay mechanism including a transistor Q36 (e.g., Part No.MJD112, manufactured by Fairchild Semiconductor®, among others) and aresistor R186 (e.g., about 470 ohms). The SS relay drive 409 can receivesignals from the microcontroller circuit 410 via a connection 512. Thebase of the transistor Q36 can be connected to the resistor R186 and theemitter of the transistor Q36 can be connected to ground. When a signalfrom the connection 512 applies a substantial cut-in voltage across thebase-emitter junction, the transistor Q36 becomes active and allowscurrent flow from the collector to the emitter. The current flow canprovide a path for a return connection 514 from the external circuitthrough the collector and the emitter to ground. With the active returncurrent path to ground, the external circuit can be powered by voltageV15 via a connection 516. Without the signal from the microcontrollercircuit 410 at the connection 512, the external circuit can remainwithout power (i.e., switched off). In some embodiments, the externalcircuit can be a heater or relay.

FIG. 20I illustrates the microcontroller circuit 410 of the controlcircuit 361. The microcontroller circuit 410 can incorporate themicrocontroller U26, which can include a microprocessor and/or a digitalsignal processor, a digital-to-analog converter and an analog-to-digitalconverter. In some embodiments, the microcontroller U26 can be a digitalsignal controller, such as Part No. MC56F8025, manufactured by FreescaleSemiconductor®. The following paragraphs describe pin assignments forthe microcontroller U26 according to one embodiment of the invention.

The connection 482, which is the receiving line of the serial port inthe memory/external ports circuit 406, can be connected to pin 1 of themicrocontroller U26. The connection 488, which is the data line of theI2C bus line to the memory/external ports circuit 406, can be connectedto pin 2 of the microcontroller U26. The connection 484, which is thetransmission line of the serial port in the memory/external portscircuit 406, can be connected to pin 3 of the microcontroller U26. Pin 4of the microcontroller U26 can output voltage V25, which can transmittedto the latch U23 in the alarm circuit 404. Pin 5 of the microcontrollerU26 can receive voltage V22, which is the output from the multiplexerU22 in the tachometer circuit 402. The connection 498, which is inputline to the remote unit in the memory/external ports circuit 406 can beconnected to pin 6 of the microcontroller U26. The connection 420, whichis an input from the sensor S9 of the temperature sensors circuit 398,can be connected to pin 7 of the microcontroller U26. Pins 8, 9, 10, 37,and 38 of the microcontroller U26 can be open. Pins 11, 29, 35, 16, 23,and 12, 17, 28, and 36 of the microcontroller U10 can be connected to acapacitor circuit including capacitors C95-C99 in connection with thevoltage V14 (pins 11, 29, 35, 16, and 23) and ground (pins 12, 17, 28,and 36), with the configuration shown in FIG. 20I. The capacitors C95and C97 can each have a capacitance of about 1 microfarad, thecapacitors C96 and C98 can each have a capacitance of about 0.1microfarads, and the capacitor C99 can have a capacitance of about 10microfarads.

The connection 418, which is an input from the temperature sensor S8,can be connected to pin 13 of the microcontroller U26. The connection416, which is an input from the temperature sensor S7, can be connectedto pin 14 of the microcontroller U26. The connection 414, which is aninput from the temperature sensor S6, can be connected to pin 15 of themicrocontroller U26. The connection 412, which is an input from thetemperature sensor S5, can be connected to pin 16 of the microcontrollerU26. The connection 504 from the programming interface 408 can beconnected to pin 19 of the microcontroller U26. Pin 20 of themicrocontroller U26 can output voltage V26, which can transmitted to thelatch U23 in the alarm circuit 404. The connection 510 from theprogramming interface 408 can be connected to pin 21 of themicrocontroller U26. Pins 22, 23, 24, 27, and 31 of the microcontrollerU26 can output the voltages V24, V23, V17, V18, and V19, respectively,which can all be transmitted to the power circuit 360.

Pin 25 of the microcontroller U26 can output voltage V27, which can betransmitted to the latch U23 in the alarm circuit 404. The connection500, which is input from to the remote unit in the memory/external portscircuit 406 can be connected to pin 26 of the microcontroller U26. Theconnection 486, which is the clock line of the I2C bus line to thememory/external ports circuit 406, can be connected to pin 30 of themicrocontroller U26. The connections 430, 432, 434, and 436 from the fanspeed control circuit 400 can be connected to pins 40, 39, 32, and 33,respectively, of the microcontroller U26. The connections 508, 502, and506 from the programming interface 408 can be connected to pins 41, 43,and 44, respectively, of the microcontroller U26. In addition, theconnection 512 from the SS Relay Drive 409 can be connected to pin 42 ofthe microcontroller U26.

It will be appreciated by those skilled in the art that while theinvention has been described above in connection with particularembodiments and examples, the invention is not necessarily so limited,and that numerous other embodiments, examples, uses, modifications anddepartures from the embodiments, examples and uses are intended to beencompassed by the claims attached hereto. The entire disclosure of eachpatent and publication cited herein is incorporated by reference, as ifeach such patent or publication were individually incorporated byreference herein. Various features and advantages of the invention areset forth in the following claims.

1. A thermal management unit for an enclosure, the thermal managementunit comprising: a housing; at least one fan to direct air flow throughthe housing; a plurality of thermoelectric modules; at least one heatsink assembly coupled to the plurality of thermoelectric modules; acontroller providing power to the plurality of thermoelectric modules;and a printed circuit board incorporating the plurality ofthermoelectric modules and electrically connecting the plurality ofthermoelectric modules to the controller, the printed circuit boardseparating an ambient side of the thermal management unit and anenclosure side of the thermal management unit.
 2. The thermal managementunit of claim 1 wherein the plurality of thermoelectric modulescomprises a first plurality of thermoelectric modules positioned in anarea of higher air flow in the housing and a second plurality ofthermoelectric modules position in an area of lower air flow in thehousing, wherein the controller provides higher power to the firstplurality of thermoelectric modules and lower power to the secondplurality of thermoelectric modules.
 3. The thermal management unit ofclaim 1 wherein the controller further provides power to the at leastone fan using pulse width modulation.
 4. The thermal management unit ofclaim 3 wherein the controller modulates the speed of the at least onefan in substantially real-time.
 5. The thermal management unit of claim4 wherein the at least one fan includes at least one enclosure fanpositioned in the enclosure side of the thermal management unit and atleast one ambient fan positioned in the ambient side of the thermalmanagement unit, wherein the controller individually modulates the speedof the at least one enclosure fan and the at least one ambient fanseparately.
 6. The thermal management unit of claim 1 wherein the atleast one heat sink assembly includes an ambient heat sink on theambient side of the thermal management unit and an enclosure heat sinkon the enclosure side of the thermal management unit.
 7. The thermalmanagement unit of claim 1 wherein the at least one fan includes anambient fan on the ambient side of the thermal management unit and anenclosure air fan on the enclosure side of the thermal management unit.8. The thermal management unit of claim 1 wherein the controllerprovides regulated voltage levels to the plurality of thermoelectricmodules.
 9. The thermal management unit of claim 1 wherein the pluralityof thermoelectric modules includes one of four, eight, twelve, andsixteen thermoelectric modules.
 10. The thermal management unit of claim1 wherein the ambient side of the thermal management unit and theenclosure side of the thermal management unit are positioned inside theenclosure, and the ambient side is in communication with air outside theenclosure.
 11. The thermal management unit of claim 1 wherein theambient side of the thermal management unit is positioned outside of theenclosure and the enclosure side of the thermal management unit ispositioned inside of the enclosure.
 12. The thermal management unit ofclaim 1 wherein the ambient side of the thermal management unit and theenclosure side of the thermal management unit are positioned outside theenclosure, and the enclosure side is in communication with air insidethe enclosure.
 13. The thermal management unit of claim 1 furthercomprising a thermal transfer material applied at an interface betweenthe plurality of thermoelectric modules and the at least one heat sinkassembly.
 14. The thermal management unit of claim 1 further comprisinga tachometer to measure a speed of the at least one fan, the tachometerbeing in communication with the controller.
 15. The thermal managementunit of claim 1 wherein the printed circuit board includes electricalconnections to at least electrically connect the controller to theplurality of thermoelectric modules, the electrical connections beingpositioned on the enclosure side of the thermal management unit.
 16. Thethermal management unit of claim 1 further comprising at least onetemperature sensor in communication with the controller.
 17. The thermalmanagement unit of claim 16 wherein the at least one temperature sensoris a thermistor and is positioned to monitor temperature of the air flowthrough the housing.
 18. The thermal management unit of claim 17 whereinthe at least one temperature sensor is positioned along at least one ofan inlet of the ambient side of the thermal management unit, an outletof the ambient side of the thermal management unit, an inlet of theenclosure side of the thermal management unit, and an outlet of theenclosure side of the thermal management unit.
 19. The thermalmanagement unit of claim 1 wherein the controller is adapted to change apolarity of the power to the plurality of thermoelectric modules. 20.The thermal management unit of claim 1 further comprising an alarm incommunication with the controller, the alarm being activated by thecontroller when the controller senses a fault in the thermal managementunit.
 21. The thermal management unit of claim 20 wherein the alarmincludes at least one of a visual alarm and an audio alarm.
 22. Thethermal management unit of claim 1 further comprising an externalcommunication link connected to the controller.
 23. The thermalmanagement unit of claim 1 further comprising one of an RS-232 port, anI2C communications port, an RS-485 port, a USB port, and an ETHERNETport connected to the controller
 24. A thermal management unit for anenclosure, the thermal management unit comprising: a housing; at leastone fan to direct air flow through the housing; a first plurality ofthermoelectric modules positioned in an area of higher air flow in thehousing; a second plurality of thermoelectric modules position in anarea of lower air flow in the housing; a first heat sink assemblycoupled to the first plurality of thermoelectric modules; a second heatsink assembly coupled to the second plurality of thermoelectric modules;and a controller providing power to the first plurality ofthermoelectric modules and the second plurality of thermoelectricmodules, the controller providing a higher power to the first pluralityof thermoelectric modules and a lower power to the second plurality ofthermoelectric modules.
 25. The thermal management unit of claim 24further comprising a printed circuit board incorporating the firstplurality of thermoelectric modules and the second plurality ofthermoelectric modules, the printed circuit board electricallyconnecting the first plurality of thermoelectric modules and the secondplurality of thermoelectric modules to the controller, the printedcircuit board separating an ambient side of the thermal management unitand an enclosure side of the thermal management unit.
 26. A thermalmanagement unit for an enclosure, the thermal management unitcomprising: a housing; at least one fan to direct air flow through thehousing; a plurality of thermoelectric modules; at least one heat sinkassembly coupled to the plurality of thermoelectric modules; acontroller providing regulated power independently to at least one ofthe plurality of thermoelectric modules to optimize thermal managementunit performance; and a printed circuit board incorporating theplurality of thermoelectric modules and electrically connecting theplurality of thermoelectric modules to the controller, the printedcircuit board separating an ambient side of the thermal management unitand an enclosure side of the thermal management unit.
 27. A thermalmanagement unit for an enclosure, the thermal management unitcomprising: a housing; at least one fan to direct air flow through thehousing; a plurality of thermoelectric modules; at least one heat sinkassembly coupled to the plurality of thermoelectric modules; acontroller providing power independently to at least one of the at leastone fan to vary airflow to the plurality of thermoelectric modules andthe at least one heat sink assembly to optimize thermal management unitperformance; and a printed circuit board incorporating the plurality ofthermoelectric modules and electrically connecting the plurality ofthermoelectric modules to the controller, the printed circuit boardseparating an ambient side of the thermal management unit and anenclosure side of the thermal management unit.